Reply #6: It'd be tough to put him in.

[Kutjara]

The other cast members who'll be making cameos are "still alive" in the sense that they weren't killed off in the series or subsequent movies. Therefore, their appearances in the movie can be in the form of "flashbacks" or "reminiscences" from some arbitrary time after the movie's main events. It doesn't matter that they all look much older than the last time they appeared on screen - it's just happening many years later.

Kirk, unfortunately, died in Star Trek: Generations, when Shatner was in his early 60s. It would take some major retconning to explain a 75 year old Kirk making an appearance in the new movie. The scenes can't take place after he's dead (presumably), but setting them any earlier in the ST timeline would raise the question of why he looks so much older than the day he died.

I think the producers just decided to sidestep the issue altogether.