I am 100% ok with John Williams doing Episode VII. I just hope it doesn't have a whole new feel to it like the PT had. The original trilogy scores were epic and had so much emotion, and everything blended together well. I didn't feel that way about the prequel trilogy in most cases. I am not blaming John Williams though. Look what he had to work with. I think the music might have been fine if the movies were great. An example is when Adywan used PT music in Revisited during the Obiwan duel, it really worked well and was exciting.

Regarding Man of Steel, I have mixed feelings about it. Initially I liked the idea of Superman Returns using the music, but after seeing the movie, it felt out of place. I associate the music with the Christopher Reeve films. Superman Returns wasn't really part of those films although it had a lot to do with them. Man of Steel is a complete reboot, so after going through it with Superman Returns, I feel that a new score is the right choice. With that being said, this is pretty awesome (blend of John Williams score): http://www.youtube.com/watch?v=fvdBvJi_eRQ