LoneStranger said:
Here's the answer.
The Enterprise NCC-1701, having one of the most awesomest crews in Federation history, gets a dedicated wing in the San Francisco branch of the Federation Museum.
A hooded Old Ambassador Spock is slowly walking down the hallway as images play on the walls depicting historical moments with the crew from TOS episodes and the movies. He pauses to watch a few of the scenes as they play out, and looks over some displays showing their old belongings, like Kirk's glasses.
As he gets to the end of the exhibit, he enters a dimly lit lecture hall where there are a handful of people watching a holographic recording of Old Kirk giving a lecture from one of his classes late in his career (probably just pre-GEN). What makes this lecture stand out is that he is asked a question about what it meant to him exploring the galaxy. While Old Kirk mentions the interesting new things to be discovered, he says that the most 'facinating' part was taking everything they learned about the rest of the galaxy and using it to truly understand what it means to be a human being. Old Spock, in a moment of Vulcan weakness, sheds a tear.
I could see this be the end of the movie, before they fade-flash back to the Young Kirk in charge of the Enterprise, getting ready to go into warp, with his new buddies Spock and McCoy next to him.
It's a cameo, which is about all Shatner could expect at this stage of production. It's a 'surprise' for the casual folks who didn't know much about this movie but still know who Shatner was, and it's a chance for all the hardcore fans to cheer in the middle of the theater.