Our thanks to AMC's SciFi Scanner. That site spoke with Star Trek director J.J. Abrams, who discussed why fans won't see William Shatner reprising the role of Captain James T. Kirk in the May 2009 movie:
Q: How do you react to William Shatner's ire at not having a role in the movie?
A: It was very tricky. We actually had written a scene with him in it that was a flashback kind of thing, but the truth is, it didn't quite feel right. The bigger thing was that he was very vocal that he didn't want to do a cameo. We tried desperately to put him in the movie, but he was making it very clear that he wanted the movie to focus on him significantly, which, frankly, he deserves.
The truth is, the story that we were telling required a certain adherence to the Trek canon and consistency of storytelling. It's funny -- a lot of the people who were proclaiming that he must be in this movie were the same people saying it must adhere to canon. Well, his character died on screen. Maybe a smarter group of filmmakers could have figured out how to resolve that.
The original James T. Kirk won't appear in next year's Star Trek movie.