well, at least some of the pre-ANH material is out there, right? i've never read it but there's that early draft of "the star wars" from the early seventies that's on many websites. so it's possible to legitimately trace at least some of what lucas knew in those early days.

my personal feeling is that he may have had some sketchy idea of IV-VI, but that the prequels were almost certainly an invention of the mid-nineties. certainly nothing close to the nine-episode saga he claimed was in his brain after the success of "star wars." savvy bit of marketing there, george, claiming you have EIGHT other star wars movies in your head as soon as the first one is a smash hit...but i'm not legitimately buying it.