This was the best superhero movie because there were no gay superpowers in it. Every other superhero movie either has to do with the character coping with his/her newfound powers or society doing the same. Here we get a much more meaningful look at the relationships between three individuals (Batman, Dent and Gordon); how they each view one another as part of that society and how ultimately trust is misplaced in the hands of one of them.

[spoilers]In the next movie the Joker will be explained away; a life sentence at Arkham or some such. Two-face is probably not dead. Gordon and Batman agreed to keep him away so that his image as Harvey Dent could live on in the public consciousness.[/spoilers]

Really as long as they don't introduce Robin or Catwoman, and they don't have some of the lamer villains like Mr. Freeze, the next movie should be fine.