Here's the deal. Before 7, 8 and 9 get done, he wants to do over the original trilogy with all computer animation...including the actors! He's a crazy, old man but whatever is what I say.
He did it in such a weird order because he was making up everything as he went along. The idea for A New Hope came along, and he had to create some past to it all to give the movie some background. It wasn't until he wrote The Empire Strikes Back that Luke's father, Anakin, was Vader. A lot of the stuff he wrote was made up on the spot. That's why many point out the plot errors that have come about (I'm not gonna list them).
Can't wait to see Episode 3. Been reading the revised scripts for it for over a year now, and now it's going to come to pass. Sweet! I'm one of those that waits til later to see it when the theater is half-full.
Stefan