I've been left with the same impression, that the film has been locked editorially far earlier than either of the other PT films, and JW has had a better shot at scoring to picture. There's no discussion of newly added scenes, and all the pick up sessions being filmed seem to be inserts, continuity, and the like. I even think they were making a concerted effort to lock
for him to do his work, which is a shock.
Pablo mentions some good tidbits in a follow-up on Hyperspace that discussed the Obi Vs Anakin duel’s music and an album arrangement. It’s apparently a new theme that was memorable enough for him to be humming later in the day. Also sounds like a chorus are coming in on it and it recalls lots of other themes as they duel, and is punched up with a lot of brass and “military nobility”. But the important news is that it is most certainly scored to events on-screen, dipping for dialog moments and punctuating important dramatic moments. Sure sounds like he is working under better conditions than AOTC.
I think the whole bailout on the Main Theme could be a money issue, like shaving a day off the scoring sessions. That had better mean that there's a lot of new cues being recorded that ate up there studio time and budget instead. The first thing that I imagined when reading that was a horrible edit right at the start of the movie. All the previous chapters have had nice, subtle transitions from the Main Theme to the on-screen events during the starfield pan, all unique. I hope they do a good job matching things up transparently. If not, Ben Burtt can track in a Muppet voice in the space battle yelling “Poodoo!” to cover it up.

I'd like those 2-CD sets as well, done properly. That TPM 2-discer is a joke. But first the scores have to be finished. I consider AOTC’s final 20 minutes nothing but temp tracks at the moment.
I’d 100% support some score revisionism, ala Peter Jackson and Howard Shore on the LOTR extended editions. I’d like them to revisit the prequel trilogy on DVD or HD-DVD, with all the changes he’ll likely feel needs to be made once this is all over, and then let John Williams back in for a clean-up pass to the score. Fork out the cash for a couple days with the LSO. Have him tweak the pod race in TPM, and then sort out the mess made of AOTC, and actually score the final 20 minutes. That would be something really special.