Attempting to jump through a bunch of hoops in order to 'rationalize' the character's real name being something other than what it was said to be is completley unnecessary. Nolan and Co. were able to pay homage to the Robin character (and the myriad individuals who have worn that mantle) without compromising their vision for the trilogy and the tone that they had established back with Batman Begins, and they did so flawlessly.
BTW, here's my full review of the movie:
The film is the best of Nolan's trilogy (although it's not nearly as epic as TDK [nor does it have to be]), and the perfect capper to this particular on-screen iteration of the Batman mythos (albeit leaving the door open to some type of future continuation should Warner Bros. decide that they want to go forward without Christopher Nolan and Christian Bale).
I also need to give Nolan props for masterfully re-using the same twist from Batman Begins, but doing so in a way that was not in any way repetative. I think most of us Internet fans figured out that Miranda was Talia long before the film actually came out, but the way Nolan used the 'Bane is an al Ghul' red herring managed to leave the Miranda = Talia reveal enough 'oomph' that it didn't feel anticlimactic.
Back when the first press release for TDKR was released and we found out that Selina Kyle/Catwoman would be involved in the film, many people were quick to call her a villain, which is something that I resisted doing. It turns out that I was right to not call her a villain, because she wasn't; she was an antagonist
(which is not the same thing as a villain), in that she wasn't willingly working for Bane. She did lead Bruce into a trap, but she didn't do it out of spite or malice.
I've seen people elsewhere trying to rationalize a way in which John Blake's real name could have been Richard Grayson, but I think such 'hoop jumping' is completely unnecessary. Nolan and Co. managed to pay homage to the Robin character without compromising their vision for what they wanted their trilogy to be, and they did so flawlessly. There is absolutely no reason why the Nolan-verse 'Robin' had to be one of the characters who occupied that mantle in the comics, because Nolan and Co. were able to get the same message across.
FWIW, though, I genuinely believe that the way things were ended pretty heavily implied that Blake was eventually going to take up the mantle of Batman from Bruce rather than adopting his own costumed identity to continue Bruce's legacy of protecting the city.