I don't think the pressure is any greater than it was. Clearly the next Superman movie has to perform better than the last one, and be much more of the "crowd pleaser" that the studios are looking for, but it's not going to be considered a failure if it doesn't do TDK-type numbers.
If anyone is up to the challenge though, I think it's Singer. No matter what your opinion of SR, he's one of the few superhero directors out there besides Nolan who could be considered a real artist.
While other directors are simply making flashy, live-action cartoons, Nolan and Singer are actually trying to bring something interesting and complex to the table.