I've been wondering lately if the Apple TV ship date may be dependent on Apple's progress in other areas-- specifically, the iTunes store.
It seems odd to me that the Apple TV specifically requires a widescreen television when widescreen content isn't available at the iTunes store. Perhaps widescreen content-- or, better yet, real 720p content-- will become available at the same time as the new device?
I think there's still a piece of the puzzle that's missing, and that may be it. I know the movie trailers are available in 720p, but not even Apple could get away with charging $300 for a device designed only for trailers.