For what it's worth, I think we were supposed to see the potential for old Kirk in NuKirk in the scene where he, Sulu, and Olsen do the space jump. From everything we'd seen so far, if anyone was going to be irresponsible and get himself killed, it seems like it would have been Kirk. However, he completed the mission in a way that one could assume is pretty much by the book, indicating that for all of his bluster and tendency to spout off, there's a guy in there that took his training at the Academy seriously enough to care about learning to do things correctly.
For me his promotion wasn't a big deal. Obviously there was only one way to end such a movie and that was going to be with Kirk taking command of the Enterprise. Yes, it could have been made a little more plausible if they'd stuck a "two years later" over the scene, as someone suggested, but, as someone else suggested, the events we are shown don't necessarily HAVE to have happened immediately. To me it's ambiguous enough to be a moot point.
For me his promotion wasn't a big deal. Obviously there was only one way to end such a movie and that was going to be with Kirk taking command of the Enterprise. Yes, it could have been made a little more plausible if they'd stuck a "two years later" over the scene, as someone suggested, but, as someone else suggested, the events we are shown don't necessarily HAVE to have happened immediately. To me it's ambiguous enough to be a moot point.