Can't really see the villain being a huge factor anyway. The first story was all about Batman's origins, Liam Neeson's bad guy was pretty interchangeable but that was fine, the story wasnt about that.
Then the second film was THE big bad villain story. I can't see anyone outdoing Heath's performance and I think Nolan will try to take emphasis away from focusing on the bad guy.
I know Tom Hardy is a great actor, Im sure his performance will be stellar but to me I don't really care who the villain is, I don't think the movie will be centered around it.