According to original series star Mark Hamill, though, that decision had already been made at Lucasfilm over the summer, when George Lucas met with Hamill and his co-star Carrie Fisher to inform them that Star Wars Episodes VII through IX were being developed.
"I thought he was going to talk about either his retirement or the Star Wars TV series that I’ve heard about — which I don’t think we were going to be involved in anyway, because that takes place between the prequels and the ones we were in and, if Luke were in them, he’d be anywhere from a toddler to a teenager so they’d get an age-appropriate actor — or the 3-D releases," said the actor in an Entertainment Weekly interview. "So when he said, 'We decided we’re going to do Episodes VII, VIII, and IX,' I was just gobsmacked."
Regarding the films themselves, Hamill said he had no idea whether Lucas ever intended for the pair to be involved, saying only that Lucas wanted to let them know that they would be made, and that Lucas wouldn't be directing them. The filmmaker them reportedly swore Hamill and Fisher to secrecy.
As for the sequels themselves, you could say that Hamill is cautiously optimistic.
"I can see both sides of it. Because in a way, there was a beginning, a middle, and an end and we all lived happily ever after and that’s the way it should be — and it’s great that people have fond memories, if they do have fond memories," Hamill said. "But on the other hand, there’s this ravenous desire on the part of the true believers to have more and more and more material. It’s one of those things: people either just don’t care for it or are passionate about it. I guess that defines what cult movies are all about."