In the last couple of months there's been a lot of reports and a speculation that The Riddler would be the villain (or at least one of the villains) in the third Batman movie, and more recently rumours emerged that Joseph Gordon Levitt was Christopher Nolan's choice to play the role.
The problem with all this speculation is that it was based on very scant evidence, as no one was officially saying anything. Much of the time it appeared to be a bit of a house of cards, where people saying The Riddler would make sense as the next Batman villain morphed into reports that The Riddler would be in the film, despite no real evidence. From there, it was only a short jump to wondering whether Levitt, who's just worked with Nolan on Inception, might be up for the role.
However now some actual evidence of both The Riddler being in the film and the possibility of Joseph Gordon Levitt playing him has surfaced. FirstShowing managed to get hold of the casting grid for the film, which confirms The Riddler as being the villain, and shows that Levitt is interested (which is a long way from saying he's going to do it, but it's a step in the right direction).
As First Showing points out, 'A casting grid is used in the industry to keep production companies, agencies, etc. in the loop on a project's progress and the roles available for actors to potentially take. These documents are used for business planning in the industry and by no means would use internet speculation to list a character that may not even appear in the film. But when it comes to listing actors, this is info that can change at anytime, and just because an actor or studio is interested in one or the other, does not mean it will actually happen.'
However, while the casting of the role may change, it seems as if this is confirmation that Riddler will be in the third Batman movie.