It looks to be a given that Mark Hamill, Carrie Fisher, and Harrison Ford will be a part of Star Wars: Episode VII in some capacity. Just how much remains to be seen, even with the story possibly involving their characters' kids. All three have expressed a desire to return, and according to some its already a done deal, but George Lucas chimed in during a piece in Bloomberg that suggests he had them signed long ago.
Lucas: "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.'"
After that, he seemed to realize he might have made a boo-boo by spilling the beans.
Lucas: "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."
I bet they were. We already knew he had spoken to Hamill and Fisher about it the summer before the Disney deal, so this basically just closes the loop on that. There probably hasn't been any formal signing yet, just handshake agreements and what not.
When a deal is finally struck, it'll likely play out just as Lucas suggests, with balloons and champagne and Star Wars video blogs, etc. etc.
