I've watched a lot of interviews with Lucas.  Originally, Lucas said he was going to make a total of nine Star Wars movies--the "first" triology about Annakin Skywalker and his descent into evil and end of the Republic, the second which was actually the first triology made, and a third about the post Empire new Republic.  I think, given the age of the original actors, they'd do best to do a Star Wars, the Next Generation--perhaps about Leia's and Han's Solo's children and possibly Luke as a Jedi Master Guru.

Truth be told I loathe the "first" trilogy--Anakin was never a very sympathetic character even before he became corrupted.  I think if someone besides Lucas could write the next trilogy it could be good, but it seems to me that he was struggling to come up with material during the prequel.  Almost everything in it was begged, borrowed or stolen from Edgar Rice Burroughs Mars series to Ben Hurr.  I have a pretty good suspension of disbelief when it comes to such things, but even I couldn't buy Luke and Leia's mother dieing of a broken heart after childbirth. . .