skyjedi2005 makes many good points in his post. Lucas made a big mistake using those HD cameras for the most recent movies. Sometimes I think he does stuff like this just because it's new and "cutting edge", just for the sake of it being so, even if the end result is inferior in quality. Just because something is newer, doesn't mean it's better. Ironically, it's The Phantom Menace, the first of the prequels, that looks the best. And it will always have vastly more resolution than Episodes II and III.
And The Phantom Menace will look better on Blu-Ray when it's released, since they will be scaling it down from a much higher res scan. When they do the new archival scan in preparation for the Blu-Ray release, it will probably be a 6k scan (4k minimum), maybe even an 8k scan (hadn't heard of those before, must be the very latest super high-end scanner for films :) ).
Thank God at least The Lord of the Rings trilogy was shot on real film. That would have been a catastrophe with an HD camera. :)
As for the Wookiegroomer sets, the 12 gig HD ones already look great and I thank him for making them. :) Even taking into account adding in the extra soundtrack options and the tri-screen comparison video's inclusion, I don't see how color correction could account for the video going from 16 or 17 gig up to 45 gig. I mean, the video was already 1080p to begin with (not Blu-Ray quality, of course, but the best quality 1080p broadcast version so far), so there was no need to up-res it for watching on a high definition TV.
So I'm not sure what good it would do to crank up the bit-rate really high and get a huge video, as you can't get more detail than the original source video had. You'd think a 25 gig single-layer Blu-Ray disk would be plenty large enough to handle the color corrected video along with the soundtrack options and the tri-screen comparison. Maybe the video and all the soundtracks went just a little long to 26 gig or something, and he figured, "What the heck, I'm already into the second layer, might as well really crank the bit-rate and make full use of that 50 gig disk."? :) Or perhaps he felt a really high bit-rate was necessary to prevent any further compression artifacts from being introduced to the original video when he did the re-encode to have the color correction in place? Maybe it was necessary. You certainly wouldn't want to deteriorate the excellent quality of the source video.