Re: Why did the League of Shadows want to destroy a peaceful city?
However, I would say that Gotham is somewhat 'cured' by the end of TDKR, or at least on the path to being so. Unlike before, with Dent and the 'peace-time', all the city's long-standing problems/evils (economic inequality) have had their chance to surface, however violently they did, and presumably will be addressed (as the city has seen what it could lead to). It's not unlike the psychology of a person. Deep and unresolved issues have to be resolved for there to be true peace, etc. ("things were always going to get worse before they got better").
Bruce has also given the city its true symbol of hope, shaking them out of apathy.
This is also why I'm fine with Blake receiving the mantle when he does. I don't think Gotham will need him for a long time (and by then he'll by all trained up). He will only need to step in if and when the city loses hope and the police are unable to do things themselves.