You're forgetting that high bitrate is not the be-all, end-all of quality. In fact, if you ask most compressionists, it's what you DO with those bits. That's why the Superbit discs don't fill the volume.
Guys, Blue-Ray is a format, not a compression style.
MPEG-4 is a great format, I'll wait till I see some actual video in the new format, but I'd say it'll be fine. It doesn't matter what kind of disc they use, it's what you do with those bits! Encode a video clip in MPEG-2 on your computer...