If you can all excuse the length of this post, I'd like to share why and how I feel Batman dying could 'work' in some way. And why, admittedly, it would be difficult to achieve and ultimately unlikely. The reason why I point to Miller's Dark Knight Returns as possibly the only way it could work is because it's executed along some pretty vital parameters....and I believe they'd have to be met in the movie to work, too.
1.
The hero is a martyr by choice. He has to foresee some sort of concrete benefit of his being dead, or being perceived to be dead. It has to be a calculated outcome, and not just the less-desirable result of the same risk he takes night in and night out. The Hero has to believe that it's the best way to ultimately achieve his larger goal. Otherwise, his death is just him dying...and its only function is that of tragedy/sympathy.
2.
The hero can't die fighting a villain. He has to be fighting something that needs redemption and something that needs changing into something else, or something good that it used to be. He can only die not just saving who he's protecting, but saving who/what he's actually fighting. That's what gives his sacrifice true meaning.
3.
Something has to already be in motion. Batman needs to have the utmost confidence that someone or something will carry on his mission after he's gone..and we have to see it already underway. Otherwise, if it's 50/50 or what have you, it's almost negligence and abandonment on the hero's part if he knows that his guidance and inspiration will still be needed.
In Dark Knight Returns, Batman 'died' while fighting Superman...not Joker, not Bane, not Killer Croc. He died fighting the hero of all heroes, because what Batman was really fighting was the system that the people needed to believe in. What's the point of fighting evil if there isn't a greater good to have faith in? He was fighting a system that he believed could turn around, but would never forgive him for turning it around. There would always be that conflict, so he decided that by removing himself from the equation (after he took care of business, of course), it would ultimately streamline its path towards a higher road. And Batman fully accepted death as an outcome...he had to in order to have a chance of fighting Superman and to wake him up. The only way to get to his destination was not to save anything for a trip back. The Batcave and mansion were destroyed, his personal fortune liquidated....there was no turning back. He chose this outcome, it didn't just tragically happen.
And the signs were there that the people had finally 'caught on'. It was incited by a cataclysm...a huge electromagnetic power outage that caused disasters and anarchy in the streets. But with his help, the city stepped up and banded together. They relied on eachother, and gave to help/potect others. It was something that would bring them together and keep them together like nothing before. The wheels were in motion.
So something along those lines is really the only way I could see Batman dying in TDKR, and having it be a logical, satisfying, and narratively responsible as an end to the story....even without him secretly surviving like in Dark Knight Returns. Otherwise, it could too easily be as cheap as some are fearing it would be...shock value over true narrative substance and so on. This is a hero story, after all...and if you as the storyteller believe in what the hero stands for, then his death has to stand for something in how it's planned out and executed. A hero's death has to celebrate/cement his life and his purpose, not lament his passing.
This is why I think Miller's approach in Dark Knight Returns is perhaps the only way (or at least the best way) it could work (granted, I haven't read a whole lot of Batman comics). It's also why I feel he p*ssed all over it with The Dark Knight Strikes Again.
But I don't know if Nolan's Batman has the 'elbow room' for something on that scale....never mind there being no Superman. Some feel that this is still just the early years of Batman, and there's much more work to be done until the end should sensibly arrive. I think that these three movies can feel like a lifetime without having to span any more than the 7-10 years of his being Batman. But I can also understand that some may need to sense more of a twilight of his career before even considering the 'end'. Chances are, Batman won't die in TDKR....but I'd still be interested in seeing how it would be handled.
Sorry for the rambling, y'all.