Yes, JGL is in TDKR! Or at least, he looks to be pending official confirmation. Speculation is already running rife as to who he might be playing just as it did back when word of Tom Hardy being cast hit. And just like Hardy there are several characters Levitt could potentially fit.
Some seem to think he will be The Riddler even though Nolan already said he won't be in the movie. Was he misleading us? Highly unlikely, although what about a variation on the character. Edward Nashton maybe? Levitt seems to young for Dr Hugo Strange but that doesn't mean that the character hasn't been tweaked some. How about Black Mask? This seems to be a popular theory since there will most likely be some sort of mob boss type character in there somewhere. So how about continuing with a connection to the Falcone family. Alberto Falcone who is also the serial killer Holiday? Levitt would make a very good Robin/Dick Grayson imo but again, highly unlikely. But what about Jean Paul Valley/Azrael? It would certainly make sense if Nolan does go the
Knightfall route and takes batman out of action for a bit as recent rumors suggested he might. Or maybe he won't be playing a character from the comics at all.
The possibilities are countless. But who do you think is most likely?