Aint-it-cool-news has a story about what Natalie Portman intends on doing after Episode III. She plans to relax for a while and possibly do a movie with Luc Besson which would be a follow-up to a movie she did when she was much younger (called "Leon" or "The Professional"). She also mentioned that speculation she would play Lois Lane in an upcoming Superman movie is only a rumor but that she would be happy to play the part.