Spoilers to follow
I had a quick thought about the issue of Batman dying that was prompted by listening to the Batman on Film podcast. And I couldn't get it out on Twitter so I wanted to put it here. As I've said, I loved the ending. I've seen it three times now and it is more powerful each time. So this is really just a thought for those who aren't completely buying the ending.
What if Batman doesn't know he is going to escape and use the autopilot when he tells Selina that the autopilot doesn't work? What if that last shot of Batman in the Bat is him thinking about the decision and then finally deciding that he can let go of Batman?
He has to make a quick decision when he knows they can't get the bomb to the chamber to be deactivated. And being Batman, he knows he has to get the bomb away from the city. So he has to accept that he will die quickly because he doesn't have time to think through the other options.
What if after he says his goodbye to Gordon and kisses Selina he is finally ready to let go of Batman? Maybe that connection with Selina was enough to help him get over Rachel and convince him that he had something to live for beyond his duty to being Batman. That seems plausible enough to me.