Speaking at the investiture at Buckingham Palace, the 42-year-old said he would open to returning to the role that made him a star, Mark 'Rent Boy' Renton in the follow-up to Trainspotting.
Asked about a return to the role in a film version of Irvine Welsh's Porno, directed by Danny Boyle, he said: "I have not been approached officially, but I would be up for it and there has been talk about it happening in 2016, 20 years after we did Trainspotting.
"The sequel is called Porno, so I have to be careful about saying I am doing Porno in 2016."
But he ruled himself out of returning to the part of young Obi-Wan Kenobi in the new Star Wars sequel trilogy because the films he took part in were prequels.
Dressed in a kilt, McGregor said it had never been in doubt that he would come to the palace in traditional garb.
He said: "I didn't have to think about it, that was always what I was going to wear.
"If you don't wear your kilt here, I don't know where you are going to wear it."
The 42-year-old posed for pictures with double Olympic gold medallist Mo Farah, who was awarded the CBE at the same investiture.
The Somali-born double gold medallist, who grew up in west London, triumphed in both the 5,000m and 10,000m at last year's London Games.
Known for his trademark "Mobot" celebration, the 30-year-old picked up his honour for services to athletics after becoming one of the faces of Britain's golden summer of sport.
Speaking after receiving the award, he said: "I never in my life imagined coming to Buckingham Palace.
"I remember running past it in the mini-marathon as a kid when I was 13 and thinking it was so beautiful and taking pictures of the lion, so coming inside and receiving this award is great.
"Prince Charles said 'You must be getting sick of so many medals' and to hear someone like the Prince of Wales knows who you are is just brilliant.
"I'm not tired of it at all, I just want to make my country proud and collect as many medals in my career as I can."
He also gave Andy Murray his backing to become the first British man to win the title at the All England Club for 77 years, saying: "I believe this year he can win it."