The public may want Camilla to be Queen as she rises in people's estimation, biographer Jonathan Dimbleby has said.
The couple married in a civil ceremony at Windsor Guildhall
In an interview for the BBC's Panorama programme, Mr Dimbleby said questions still remained over the future role of Prince Charles' wife.
He also claimed the couple were denied a church wedding because the Archbishop of Canterbury did not think Church leaders would support such a ceremony.
A Right Royal Shambles? is due to be broadcast on BBC One at 2215 BST.
The programme examines the run-up to the Royal wedding, which took place in Windsor in April.
Prince Charles and Camilla Parker Bowles were married in a civil ceremony at Windsor's Guildhall, followed by a blessing at the Windsor Castle's St George's Chapel, conducted by Archbishop of Canterbury Dr Rowan Williams.
Mr Dimbleby, the prince's official biographer, said since then there had been a massive shift in public opinion.
The Duchess of Cornwall was no longer the "other woman", but was "being seen now as a very attractive spouse who makes the prince happy, who appears in public, who is gracious, who joins in - in a crowd, who communicates very effectively".
Mr Dimbleby said: "We'll see more and more of her in that role, and therefore she will go up and up in public esteem.
"It's quite conceivable that public opinion will say ... yeah, why shouldn't she be Queen, she's done a lot of good public service over the intervening years between the marriage and whenever this day arrives."
Mr Dimbleby also revealed the Archbishop of Canterbury had not allowed a church ceremony because he feared others in the Church of England would be offended.
"Although it would have been within his gift to do so, I think he took the view that there would be too many distressed communicants inside the Anglican Church for it to be a good idea," said Mr Dimbleby.
A spokesman for the Archbishop of Canterbury said Lambeth Palace had not seen the programme.
He added: "The marriage was warmly welcomed by the Archbishop of Canterbury and the Church of England at large and we continue to wish the couple every happiness for the future."
A Clarence House spokeswoman said: "Of course a range of options were considered by Lambeth Palace and Clarence House and it was readily agreed that a civil ceremony followed by a service of prayer and dedication was the best option.
"The arrangements worked well on the day and all parties were delighted with them."
Panorama is on BBC1 at 10.15pm tonight. The programme will also be streamed live from the BBC News website