During this weekend's Dragon*Con, Leonard Nimoy has announced that he will not be reprising the role of the famous Vulcan for the Star Trek sequel which is still in the writing stage.
During the Panel, Nimoy said:
There are no plans for me to return for the second movie. I think the Spock character is very well established as portrayed by Zachary Quinto. And I think if you saw the movie Bill, you'd say the same of Chris Pine.
This is sad news but it doesn't mean that he could not appear in another sequel. However, it is certain that there will be no Spock Prime in the next Star Trek movie.
You can go HERE to view the story and videos of the Shatner/Nimoy panel taken at Dragon*Con