Well, we still don't know a lot about what the new Star Wars will bring, but if they happen to be bringing any parts for hologram ghosts or one-handed, very old guys, Ewan McGregor and Samuel L. Jackson would take those. Jimmy Smits might need some more convincing.
CBS News recently asked McGregor whether he'd be up for reprising the role of Obi-Wan Kenobi, to which the actor made clear he was totally up for some more Star Wars cash to play a leering hologram or whatever, saying:
"Yeah. Of course. I mean, if they needed me, I would be up for it. Of course.
"If Obi-Wan Kenobi's in them, it can't be Alec Guinness, sadly, anymore, so I would do it. I wouldn't want someone else to do it. But maybe he wouldn't be... maybe he's not going to be in them; I don't know how that works. Maybe I'll be a hologram here or there. I don't know."
Speaking to E! on if he could come back as Mace Windu, Samuel L. Jackson too expressed his usual eagerness to collect a paycheck, and likewise thought maybe he could return to "be a ghost hologram." But, not to be limited by his own apparent death in Revenge of the Sith, he also suggested, "maybe everyone thinks I'm dead and we'll find out what happened to Mace Windu. I can come back as one-armed or a one-handed Jedi that's still around that didn't actually die," so maybe that, too. Either way works for Sam Jackson--as does anyone else someone might come up with to bring back Mace Windu, with Jackson succinctly summarizing his view on the character's future with the words, "I don't care." And as films like Snakes on a Plane, xXx: State of the Union, and Arena have shown, he truly doesn't.
Finally, as for if Jimmy Smits will return to play an aged Senator Bail Organa--even though his home planet was already exploded to show off for Princess Leia--he wouldn't make any promises, but there remains the possibility if anyone from Disney wants to give Smits a ring. Speaking to Spinoff on the subject, the actor said, "If they want to call, let them call," but was careful to remind, "My character was gone after episode whatever," which is true. That's exactly what the back of his Topps card said.