As some of you may know there was a Star Wars marathon held in London where Lucas made a surprise appearance to 1,300 die-hard fans.
"To chants of "three more films" he [Lucas] said: "This is the tragedy of Darth Vader.
"It starts when he is 9 years old and ends when he is dead. There is no more story."
A chorus of boos rang out around the cinema but Lucas quickly won the fans back over, saying: "I'm working on the next Indiana Jones."
Flanked by a garrison of stormtroopers it was a remarkable finale to a remarkable day - and the fans had yet to see Revenge of the Sith."
http://news.bbc.co.uk/1/hi/entertain...lm/4545753.stm

So it's definite now.