Though we have been told Star Trek XI -- under JJ Abrams -- will be a prequel taking us back to the good old Academy days, that doesn't mean that some of the older cast won't at least appear on set.
Abrams Talks Star Trek XI
Jam! Movies recently caught up to none other than Leonard Nimoy and discussed the upcoming Star Trek installment with the aging, but still very Spock-ish, actor. In the discussion Nimoy admits that he has been contacted by Paramount and predicts what they might have in mind for him and William Shatner on Star Trek XI.
"The head of production at Paramount called my agency to tell them about this project and they are aware of Bill's and my contribution to the franchise, and they'd like us to know they might want some involvement. It was all very, very general.
"They might possibly want Bill and I to set up the story as a flashback. But that's just conjecture on my part."
The return of Nimoy as Spock to Star Trek XI? I don't know, I would suggest we remember these characters as they were, not on how their actor counterparts look today. Be remembered as a young(er) Spock, and let Paramount do the rest.