Today, George Lucas himself confirmed that all three actors will return to that galaxy far, far away. Even though he knows he shouldn't be saying that.
Here is what he had to say to Bloomberg, explaining that the actors were in negotiations even before Lucasfilm sold to Disney.
"We had already signed Mark and Carrie and Harrison...Or we were pretty much in final stages of negotiation...So I called them to say, 'Look, this is what's going on.'...Maybe I'm not supposed to say that. I think they want to announce that with some big whoop-de-do, but we were negotiating with them...I won't say whether the negotiations were successful or not."
Star Wars: The Force Awakens comes to theaters December 18th, 2015 and stars John Boyega, Daisy Ridley, Carrie Fisher, Harrison Ford, Mark Hamill, Adam Driver, Domhnall Gleeson, Lupita Nyong'o. The film is directed by J.J. Abrams.