The European Union is expanding from 15 members to 25, and is set to grow further still in 2007.
Will a bigger EU make closer integration more or less likely? Can the EU keep on growing without becoming meaningless? BBC News Online asked eight opinion formers to share their thoughts on where the EU might be in 10 years time. Please click on the quotes below to read more and use the form at the bottom to send us your views.
Bob van den Bos is a Dutch member of the European parliament.
The main challenge for an enlarged EU is that it needs to be manageable and governable. In this context, further integration - not looser association - is the only option.
There will have to be change: Europe needs to develop a new political culture of compromise. It will happen, but it will be a slow process. I predict that on the majority of issues we will come together - the issue that is most likely to cause tensions in the immediate years to come is foreign policy, and in particular relations with the US. The newer countries are keener on stronger ties with America than some existing members are. A common European stance on the international stage may take a while to develop, but I do believe it will happen.
At the same time we will
see more power head to the European institutions. People talk about a democratic deficit as if it were getting worse, but actually it's getting better.
The European parliament is gaining in strength, and under the new constitution will develop further. Power will gradually switch from national parliaments to the European one - that doesn't mean democracy is weakening - far from it - it just means that it is changing.
I accept that this may take a while - and at present people find the idea of being represented by a foreigner difficult. But then in the Netherlands for example, people in the regions used to hate the idea of being governed from the centre. It changed, but it is a slow process.
I think after this round of expansion and the next with Romania and Bulgaria we should have a period of consolidation before going any further. We will need to take stock of what we are doing right and wrong. An EU of 35 or 40 is a real possibility, but not for a long time.
Dr Anthony Coughlan is the head of Ireland's anti-integration National Platform.
If the European constitution is rejected by some countries when it goes to a referendum there is the suggestion that a tiered Europe will be formed, with the French and the Germans leading a more integrationist group. But one wonders really who will in fact tolerate this - my feeling is that it is not sustainable in the long term.
The fundamental problem for the European Union is the fact that there is no European demos - a people who share language, culture and interests - that could give legitimacy to a democratic EU federation.
It was one thing when Germans from the West agreed to pay for the East to play catch up, but there is massive tension when this happens at a cross border level.
An EU without democratic legitimacy is in the long-term fundamentally unworkable, and I predict that what we will ultimately end up with is a loose free trade arrangement - possibly one that stretches far and wide.
Heather Grabbe is the deputy director of the London-based Centre for European Reform.
The widening of the European Union will lead to deeper integration in the long run. The EU of the future could also be more powerful. New members will bring new challenges, different things will rise up the political agenda and EU foreign policy will enter a new domain.
The new members will encourage the EU to take a new role in the world. The newcomers are very Atlanticist on defence - they want Europe to be a partner to the US, not a counter-weight in world affairs. But at the same time, they want the EU to have a more powerful role in stabilising its own backyard. They will push for an eastwards shift in EU foreign policy.
The new members will not be the poor relations for long. As Poland has shown, the accession states are ready to fight for their position in the union. There will be difficult years in the beginning, but they will rapidly become constructive partners. As they forge more concrete positions on the various EU policies and grow wealthier, they will be taken more seriously.
I think that will start to happen within about five years. We saw a similar process when Spain and Portugal joined.
Eventually, the EU will enlarge further to include Turkey and the Balkan countries. Turkey is a very strong strategic interest for the EU, and we need to adapt the EU in ways that would allow it to take in a reformed Turkey - starting with the abolition of the Common Agricultural Policy.
The European Union cannot remain the same institution it was in the 1950s - it needs to adapt and reform.
Professor Tony Judt is a scholar of European history.
The integration of Europe was driven in the post-war period by the memory of what had gone before, a common experience. But this is no longer the case; and it raises questions about whether deeper integration is really possible. I doubt it is.
The East Europeans have not only had a completely different experience from the West, they are not even being asked to join the union as equal partners. This has already created disgruntlement in a number of the new member states. Since 1989, the promise of joining the club has loomed large. Little by little however many of the promises made have been withdrawn or weakened.
That is not to say there won't be benefits from joining up - of course there will. But the kind of transformative effect that was once dreamed of is unlikely, and in many of the new states there are nationalists ready to stir up dissatisfaction, playing on the idea that those in the East have shaken off one empire only to take on another. I do not believe we will see revolts against membership, but I also do not believe that in this context there will be much enthusiasm for deeper integration.
There is no doubt that the character of the EU will change after May 1 and it cannot go on expanding indefinitely. There are also all sorts of issues thrown up by the prospect of Morocco, or Ukraine, for example, joining. But I believe Turkey will have to be taken in. People have problems with it because it means huge number of Muslims would become part of the union - and yet not to let Turkey in would send a totally unhelpful message about the benefits of Islam embracing democracy.
Carl Lankowski, who works for the US State Department, is a political scientist.
I think it is useful to take a historical view. The nation-state as we know it has been around for about 100 years, the European institutions for around half that time. As years pass, the difference of time between the two will decrease, and the European Union will seem more and more natural to people.
The model for predicting what happens should not be the 20th century state system. The history of European integration is one of innovation in design and policy. Trans-national processes are continually being innovated - that is why the EU can take on enlargement.
I think enlargement will result in a partially-constitutionalised trans-national system, a work in progress made up of both formal and informal elements.
In this sense, there the EU already has an unwritten constitution which allows for diversity and, where necessary, harmonisation. I don't see this pattern changing in the next 20 years, whether the constitutional treaty now being negotiated is adopted or not.
The new members will bring aspects that current members will have to adapt to. They will, for example, provide impulse for economic structural changes. If some of the current members do not reform their systems, investors will tend to favour the accession countries, which have reformed.
Personally, I think that in the short term there will be continuity in transatlantic relations. The US will continue to support the project of European integration as it has always done in its own enlightened self interest.
The accession of 10 countries seen as more favourable to the US will not necessarily make relations easier. On any given issue, the coalitions within the EU will be transformed as the bloc continues to develop mechanisms for common positions across the entire range of policy fields. Nevertheless, the stakes involved in continuing our partnership are too high for either side to undermine it.
Professor Jan Zielonka has written extensively on Europe.
It is hard to predict what will happen to the EU - but this notion of "ever closer union" is definitely fallacious.
Just look at the reality of what it is we have at present - major divergence between existing and future member states, which have their own different interests. The structures of some of the new member states are more comparable with America than those of Western Europe. And the EU is continuing to grow. A federal state would involve clear borders, hierarchical governing structures and a distinct cultural identity. This does not exist.
So what is going to happen? There needs to be some consensus on what the EU can do better than the nation states. It certainly can't get involved in things like welfare, it could have no role in issues such as health and education. But there are areas where it could establish itself - market issues are one obvious example. It will have to learn to improve on the things it decides to deliver, offering at least a minimum level of transparency. I foresee a much looser organisation in the future.
The EU will be one of a number of tools available to member governments, along with Nato, the UN and other coalitions. But it is not a body that in the long term will have a major influence on the course of history.
Dr Mehmet Ugur is the author of The European Union and Turkey.
Integration will still be possible with a larger EU, but it will be slower with enlargement. We are certainly not going to see any kind of federal empire though, in years to come. I predict a functional, federal structure where partial competencies may be handed to the EU - but that is the operative word - partial. Countries will not be handing over their sovereignty.
I do not believe the relationship between Europe and the US in years to come will be openly hostile. Germany does not want to go in that direction, and many of the new member states - Poland, Hungary, the Czech Republic - not to mention Turkey when it joins - have good ties with the US. But the EU will be a voice to be reckoned with. It is likely to be a voice pushing for a multi-lateral approach - one which will be keen on the involvement of the United Nations.
Will a Europe this large possibly be able to foster a European identity? Identity is such a complicated and multi-faceted issue, and depends very much on how the governments in each member state react to the EU.
The EU will never be able to stop surges of nationalism which leave it unpopular, and it will also be used as a scapegoat when things go wrong. There are also those who say that the joining of Turkey will fundamentally change the nature of the EU. Obviously the EU's Christian heritage is important, but most take a pragmatic approach. The integration of Turkey would be a good thing - it would serve as an example to all that Islam and democracy can co-exist - that would be good for both Europe and the Islamic world.
Andris Gobins is president of the European Movement in Latvia.
I think there are two possible models of what a post-enlargement European Union will look like.
The first - the one I hope for - is an EU of clear goals and strong values, which will lead to closer co-operation and a more pro-active role in the world. The other possibility is that there will be more fractures.
A more integrated future depends to a great extent on financial issues. If we increase the bloc's competencies while at the same time reducing its budget, it cannot work. And, I see worrying signals in this area.
The European Union's greatest challenge is to decide whether it wants a more pro-active role in regional and global affairs. Closer co-operation in areas of foreign policy should be an objective, but that does not mean the EU should become a federal state.
A more pro-active EU does not mean a counterpart to the US, it means being partners. The problem is not American dominance, but European passivity. I think there is a chance that EU-US relations will get stronger after enlargement - that is one of the effects the new member states will have on the bloc.
However, the most important influence the accession states will probably have is on the modernisation of the EU. The rapid economic growth experienced by the new members should be a model for some of the so-called old countries.
And, there are definitely some things which should be renewed in the EU. The accession countries have undergone many changes in recent years and are used to a fast-changing world - the Western states may find it harder to adapt.
If we take German reunification as an example, it takes a while for the contributions both sides can make to be recognised. So, it may take more than 10 years for a common understanding to be reached between new and established members.
I think, for example, the Western countries do not understand our experience of the Soviet system. We equate Communism with Nazism, but in many Western countries it is considered funky to wear Communist symbols on clothes. If the common values are reduced only to the fading Western ones or money, the new members have a smaller chance of being recognised as equal partners.
The European Union has already become more than the sum of its parts, but whether the determination to continue integration exists is hard to say. Challenges such as the Cyprus question, Turkey's possible membership and even the place of the United Kingdom could strain the Union. However, I agree with Helen Grabbe and think the EU will continue to integrate. Momentum is in that direction. That said, I do not see the EU pushing towards ever greated enlargement - I think there is a limit to its expansion, which may lie at the Ukrainian and Turkish borders.
Kit Dawnay, London, UK
I hope that the EU will become a federal state on transnational issues like defense, environment, crime, and such. It will be possible for such an EU to be democratic. Many people say there is no "European demos" now - but neither was there a British or a Dutch demos some 200 years ago. Several things can form a joint identity, such as a joint history, which Europe is definitely starting to have. Under the EU umbrella, a European demos will form and will allow a democratic EU federal state to emerge as a voice in the world. Not only as a voice, but also as an example to all the world that even 2000 years of strife and hatred can be overcome!
Willem-Jan Meulemeesters, Amsterdam, Netherlands
The next logical step for EU is the elaboration of the European Constitution which will deliver the political union that is now absent. Can you think of another action to unite 25 nations which do not share too much culture-wise? Concerning Mr Battista's comment on political correctness, of course it should be a prerequisite for entrance. Besides, isn't your government sworn duty to politically correct the world...? Why should we be any different?
Andreas Sfakianakis, Piraeus Greece
I believe the EU could potentialy be a template for integration and a model of harmonisation between an extremely diverse ethnic and cultural group of nations. If the constitution is sufficiently flexible then the EU could readily adapt to the changing economic and political circumstances which it will face in the years to come. The problem will be persuading people who are still suspicious towards the mechanisms of the EU and the process of enlargement.
The future of the EU looks uncertain. Issues with integration are of great concern within Western Europe, complete integration is an unobtainable ideology that will never work if implemented. As we grow closer to Europe and parliament loses its sovereignty people will become more tribal and territorial. The fear of losing our "identity" and the mistrust of allowing Brussels to attempt to tackle our regional concerns will ruin the EU.
Abigail Bishop, Bristol
The essential problem is, as Dr Coughlan points out, with democracy.
Until the European Commissioners are reduced to mere civil servants, accountable at a day-to-day level to democratically elected ministers under a democratically elected president, closer integration does not have a future. Europe is a group of democratic countries, many of which have had recent experience of the alternatives. We should be looking for a way to build a wider democracy, not a bureaucratic nightmare.
Simon Richardson, London, UK
The EU still has a lot to do in defining its purpose, but something it should never compromise, is its European character. In the case of Turkey, a kind of association with the EU would probably make more sense. Political correctness should not be a criteria for membership in the EU.
William Battista, Chicago,USA
Is this the way of the future with large trading blocs? The EU is nothing more then a "trading bloc" The member countries just happen to be on the same piece of land, or close by. They have no cultural connections, and in fact until recently were fighting each other! The Europe of the future will still be dominated by the UK, France and Germany and all the rest will follow. Perhaps there should have been a EU of the smaller states?
Malcolm Freeman, Melbourne Australia
Whereas the membership of many countries in the EU makes people feel a new era has begun, it is unlikely the union will produce the desired long term results. Soon separate individual national interests will collide with the good of the whole. In short it will likely turn out to be a pipe dream of idealists.
Alex Heger, Orange County, US
A common foreign and defence policy is essential if an integrated EU is to come about. It would give the EU as a whole much more power and influence than the individual member states can ever have. The lack of a common people and culture is not important - what counts is that we have a common market and shared land mass, not to mention our relatively small size as individuals. We must end our dependence on American military might to defend Europe; it isn't fair to them, and in the last analysis the defence of Europe is the responsibility of the Europeans, not Americans. A unified military capability for the EU is a long way off but I believe it is possible and we should start now. Lastly, how sad that the only country of the whole 25 which did not have official celebrations to mark the accession was the UK.
Jeff Mansfield, Hampshire UK