The vote on whether to open Croke Park to other sports or not will be decided by a secret ballot.
Rule 42 will dominate the GAA Congress at Croke Park
Fears have been expressed by those in favour of changing Rule 42 that a secret ballot could spell the death knell for Saturday's motion.
If the Rule 42 motion fails, the Ireland rugby team and Republic of Ireland football team face the prospect of playing home games in Britain.
The motion requires a two-thirds majority to get through.
The redevelopment of Lansdowne Road, which is scheduled to begin later this year, is expected to take at least three years.
During this period, the Ireland rugby team and Republic of Ireland will require another stadium for home games.
The GAA's Central Council recommended on Friday evening that Saturday's crucial vote should be a secret ballot and, while a definitive decision has yet to be arrived at, it would be unusual for the floor at Congress to go against the high-powered body's judgement.
A secret ballot could mean that a number of individual delegates might be tempted not to follow the mandated positions of their counties, which could have significant implications in a tight vote.
Twenty three of the 32 Irish counties are set to vote in favour which means the overseas votes could prove crucial.
Cavan and Donegal are the only Ulster counties to vote in favour of allowing football and rugby to play at HQ, while all six of the northern counties are against any change.
GAA president Sean Kelly is in favour of an historic change
Present estimates believe that a change will materialise, but it only takes a little sway from undecided representatives for the vote to swing back to the status quo.
A straw poll around 32 counties plus representatives from America, England, Europe and Australia puts the vote at 213 for and 78 against with 44 undecided.
Mayo are still awaiting for clarification on certain issues before their six votes are cast, a small bloc that could prove to be very decisive.
Eleven of the 17 North American votes appear to be in favour, three of the four European votes are also expected to be in favour, Australia's four delegates will decide on the day while the British vote also appear to be going for a change.
The result of the vote is expected to be announced around 1530 BST.
As regards other motions, Congress decided on Saturday morning to dispense with the clean pick-up which has been in operation during the Allianz National Football League.
It will remain in force for the rest of the National League but will then be dropped from the rules.
After the conclusion of the NFL, goalkeepers will continue to have the option of using a tee for kickouts.
Congress also decided to set-up a new arbitration body which, it is hoped, will reduce the likelihood of players using the courts to overturn disciplinary decisions.
The new Central Appeals Committee, which will officially come into existence after next year's Congress, will have a chairman and one representative from each province.