I know it's too early for this but...anyone have a guess on how these new Sony's will compare in picture quality to the Panny GS400 (IMHO the best SD consumer MiniDV cam out there)?

You're right. It's too early.

But, I expect the video quality of AVCHD at 12 Mbps to be equivalent to HDV at 25 Mbps. So, these cams should look a lot better than SD on the GS400.

Editing...now that's another story.