He has only ever said that what he originaly wrote for ANH was way to big to make into one movie, so he took part of it and made it into ANH, and then re-used a lot of his other ideas in the subsequent films. His vision was to make a serial story in 6-9 parts. He didn't have it all fleshed out, but he had ideas for what kinds of things he wanted to touch on in the movies, and then he fleshed each episode out as he made them. He was working with a rough outline of what happened before ANH, and as he finished the classic trilogy he filled in most of the blanks that were logically carried over into the prequel story.
Lucas says that originally Vader and Anakin were different people, although Anakin's was always going to be a story of a fallen hero. It's just originaly this fall from grace got him killed at the hands of Darth Vader, but then Lucas decided to take that further and have him -become- Vader. I personaly think this was the right way to go. Lucas talks about how he was always thinking of themes of redemption and of fathers and sons, and of brothers and sisters. That doesn't mean he knew going into ANH that Leia would be Luke's sister, it's just that's a theme he had touched on in previous revisions of what finally became Star Wars.
Also he has always been up front about how he hadn't decided to make Luke and Leia related until sometime during the post production of ESB.
The magazine interview from the 70's I assume you are talking about involve the idea that Lucas could make 9 or even 12 films out of the story if he wanted to. Lucas isn't denying talking about that, he's just saying that he never did come up with material for more than 6 movies. He just said he -could- possibly do 9 or 12.
I don't see any reason why he should regret telling the full story.
You guys are so far down the assumption of "history" path, you guys act like you can prove he's lying.