^ I think that your question is more than a 'possible spoiler.' I've seen the movie, so it didn't bother me, but you may just get people who haven't yet seen TDKR popping in and being hugely pissed off at the way you've phrased it all. It's too late to re-word your title but you may want to edit your post and use some spoiler code.
In answer to your question (HUGE SPOILERS AHEAD, YOU HAVE BEEN WARNED!)
Blake is not meant to be Dick Grayson, Jason Todd, Tim Drake or Damien Wayne (much less the female Robins who have helped Batman in the comics!). Nolan and Bale always said that they didn't want the character Robin in these movies. However, there is no doubt but that he is meant to be a Robin-type character and the last-minute reveal of his name acknowledged that. Like Dick he was an orphan, like Jason a street kid and like Tim he figured out who Batman was.
It's not unlike how a draft script for Batman Returns would have featured a young street kid (who would have been played by one of the Wayan brothers, IIRC), who didn't wear a costumebut helped Batman out on a number of occasions. At the end, Batman asked him his name and he said 'Robin.'
But if there is a sequel to TDKR (which I don't expect), I'd be very surprised if he was wearing a green and yellow costume and calling himself Robin. His final scene is meant to suggest that he's taking Batman's role, making the role of The Batman immortal, bigger than one man.