George Lucas in 2008 Asked if he was happy for new Star Wars tales to be told after he was gone, Lucas replied: "I've left pretty explicit instructions for there not to be any more features. There will definitely be no Episodes VII–IX. That's because there isn't any story. I mean, I never thought of anything. And now there have been novels about the events after Episode VI, which isn't at all what I would have done with it. The Star Wars story is really the tragedy of Darth Vader. That is the story. Once Vader dies, he doesn't come back to life, the Emperor doesn't get cloned and Luke doesn't get married..." George Lucas in 2012 "I always said I wasn't going to do any more, and that's true, I'm not going to do any more, but that doesn't mean I'm unwilling to turn it over to Kathy [Kennedy] to do more. I have story treatments of 7, 8 and 9 and a bunch of other movies, and obviously, we have hundreds of books and comics and everything you could possibly imagine. So I sort of moved that treasure trove of stories and various things to Kathy, and I have complete confidence that she's gonna take them and make great movies." Just thought those two quotes were very interesting. Doesn't shed much light on what caused him to change his mind however! My take is that he was very disillusioned after the PT and at first decided that he would never do any more or let any more be made. As to why he chenged his mind...I have no idea!!