Leonard Nimoy enjoyed his return as Spock this summer in J.J. Abrams's Star Trek reboot, but despite having directed Star Trek III: The Search for Spock and Star Trek IV: The Voyage Home, Nimoy told Star Trek Magazine that he won't be directing a sequel.
[Star Trek] is technically on a scale that I would be not be able to handle. The technology has increased and evolved so far beyond the kinds of things that we were doing when I was making those films. It's beyond me. It takes a certain skill and an understanding of the technology that I do not have to achieve the integration of the sets with the extraordinary special effects that are in this film.
Despite saying he would not appear in a Star Trek last month, Nimoy said he would be willing to return if Abrams asks him to.
If the phone rings again, and its J.J. calling to talk about another project, I'm more than willing to enter a discussion about it, and explore it with him. I have the feeling that my involvement has run its course — but then again, I've had that feeling many times before. I've felt that I was finished with all this, so this was a very pleasant surprised to be called back after all these years and be able to make a contribution here. If it happens again, I would glady work for him again.