Peter David stated in a recent article that Nolan had written Bruce to die in the explosion but WB veto'd it. So the whining about Bruce living happily ever after can at least stop being directed at Nolan. He was going to have him be Batman to his very last breath, not retire.
And honestly the whole "Batman quit, Batman cried, Spider-Man is emo and quit!" is about the dumbest criticism I've heard of a film and nothing I've ever come across outside of this website. Chastizing films because the hero loses his fight, gives up and then is inspired to come back with a vengeance, or lives happily ever after after saving the day. Yeah like a thousand different films haven't employed those themes across all genres. But many here get just as emo if their superheroes don't punch, punch, punch for 120 minutes without any inner turmoil at all.
Go watch Punisher: Warzone every other day and leave the real films to the grownups.