As is the case with such matters, both of the Nolan brothers have been coy about their involvement, but not necessarily quite. When asked about the film, Jonathan Nolan hinted that we will see a completely different take on Batman in this DC Comics ensemble, but he'll still be the black sheep of the family, so to speak.
The writer/producer than revealed which characters he never thought could exist in the Nolan universe version of the DC Comics world. He also explained the Robin gag at the end of The Dark Knight Rises.
It is a little hard to imagine Robin working in that universe, so the idea had to be limited to that gag at the end. But Joseph Gordon-Levitt's character is very important to the story. In any movie you need a character looking at proceedings the way you see them, and Joseph Gordon-Levitt's character is that character for this film. One of my favorite scenes is when John tells Bruce how he knew he was Batman. It's like that scene in The Prestige where the little kid sees through Christian Bale's trick. Little kids, they don't have any illusions, they just see the truth of the situation. I feel there's a kind of spiritual connection between the two movies there."
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