"Gotham needs a hero with a face."
B3 should end with the true heroes of Gotham, the heroes with a face, being established. Who were technically assumed these roles in Nolan's Batman films so far?
Batman Begins: Thomas Wayne - philanthropist, face of the people.
The Dark Knight: Harvey Dent - face of the law
It only makes sense, to me, that Bruce Wayne, after delving into the Batman persona more and more now that his "one hope for a normal life" in Rachel is gone, believing that there is no point in being Bruce Wayne anymore, comes to realise just how important Bruce Wayne is to Gotham, even more important than Batman, and he takes up the role his father assumed ("I'm going to rebuild it just the way it was, brick for brick").
And Jim Gordon, obviously, establishes himself as someone who can get the job done within the boundaries of the law, like Harvey Dent, giving the people hope in the judicial system.
As for Batman, I'm fairly sure he wont be the guy that Gotham comes to accept as their true hero, since Bruce Wayne and Jim Gordon will be that for Gotham. I honestly have no idea for what role Batman could play, but I can assume it's going to be a smaller role in the end.