Lucas said there wouldnt be any more. Personally I think its best, the best films were in the original trilogy (by far) and he didnt really direct them. He pretty much did everything for the prequel trilogy, and it ended up pathetic. Unless he hands off the series to someone younger and more talented i say he should let it be for now.
Hopefully though, someday, they will pick it back up. There are tons of Star Wars books that are very good that could be made into a movie.
