The facts :
It's not even sure at this moment that there will be a new sequel in the years that are coming. Christopher Nolan only wants to do it if the script is realy, realy strong and it has a reason of being, not just because WB wants it. He also told he has a few other projects he wants to do first and needs a break from the intense experience 'Knight' was, because it was heavy loosing Heath for everyone involved.
Ofcours the studio wants BatmanÂł to happen, because of the money. And there is no doubt that besides a thousand of fanboys and enthousiastic movie sites , the studio itself is launching this rumors.
Just to keep it alive and convince Nolan (a bit pushing, ya know)
So far we had Johnny Depp, Guy Pierce and even Jim Carrey (again) rumored as 'The Riddler'. We had Philip-Seymour Hoffman (would be great!) rumored as 'the Pinguin' and 'Angelina Jolie', 'Rachel Weisz' (most recent) and other rumored as 'Catwoman'. Oh yeah, 'Shia Labeouf' as Robin also.
The truth is that it's not even clear if one of those characters is actually going to be in the third one, IF there is going to be a third one. In fact, both Nolan and Bale don't want 'Robin' to appear in his vision of the hero. Never, ever.
I hope this clears some things out.