Apple has announced something called iFrame in a Knowledge Base article.
The iFrame Video format is designed by Apple to speed up importing and editing by keeping the content in its native recorded format while editing. Based on industry standard technologies such as H.264 and AAC audio, iFrame produces small file sizes and simplifies the process of working with Video recorded with your camera.
So it's essentially:
iMovie 8.0.5 suports it. And only two camcorders. No word on when FCP will support it.
9to5mac.com has a representational image comparing frame sizes here. Their brief article is here.
Appleinsider has a more in-depth article here.