-- Fyodor Dostoyevsky
That somehow becomes more forgivable to me if it wasn't the original ending. My complete conjecture: Christopher Nolan had Batman die at the end, but the studio made him change it because they want their Justice League movie, so Batman better be alive! To start, let's take a look at everything (I can think of) that's wrong with the ending:
- Those closest to him, Alfred, Commissioner Gordon, Lucius Fox, are left to grieve for his death. If he didn't die, isn't it sort of a dick move to put them all through that misery? Especially Alfred, whom Bruce had to know would take it particularly hard.
- If Batman works best as a symbol (something Batman himself ascribes to), then people can never know the true identity of Batman. It's not going to take a genius to piece together that Batman came out of hiding the minute Wayne came out of seclusion, then Wayne disappeared right when Batman died.
- We see Batman flying the Bat with 5 seconds left on the bomb timer. It is stated that the bomb had a 6 mile blast radius. Without using any cop outs like "the timer is shown out of sequence", and assuming Batman ejected with the full 5 seconds, that means the Bat had to be travelling 4,320 miles per hour, or in other words, well over 5 times the speed of sound, which is obviously ridiculous.
- Lucius talks to two technicians sitting in a Bat who tell him the autopilot had already been fixed. We can assume this is a new Bat, or Bane would've used it in pacifying Gotham (there's no way you don't use it if you have it), and since the R&D department was taken off the books, you know there's no legitimate buyer for which to build one, which means it was built for the sole purpose of looking at the computer log. Wait, what?
- Alfred never tells Bruce the location of the café he goes to, making it cosmically unlikely that he'd just happen to run into him. If you want to say that a man of Bruce's means could have found out the café, then we circle back around to my first point, only now it's even worse. He actually intended to let Alfred know he was alive, but let him go through the grief first!
- Batman is a hero and a martyr, but he is neither of those things if he abandons his stewardship of Gotham. Vacationing in Europe with the gorgeous Anne Hathaway? Sounds rough.
- Along with abandoning Gotham, he just hoists the mantle of Batman onto Blake without any training or even so much as a choice. If he was alive, sticking around (to thwart my second point) would allow him to train Blake, and as Bruce pointed out in Batman Begins, training was one of the reasons for his success.