Been playing with the 500D of a friend, shot some low light clips with it, video quality is very nice, but will need to go 7D for my uses.
It'd be nice to get the 500D and even the new 7D firmware hacked, there are still further things to improve apart from frame rates and manual control on the 500D that would futher raise the quality bar.
That is namely, using some kind of bicubic or lanzcos resize algorithm for pulling down the res instead of nearest neighbour, high ISO video would be even cleaner.
And fudging around with the encoder, H.264 supports up to 4:4:4 and 14-bit, since H.264 is quite efficient in terms of bitrate usage, I dont think that'd be a problem from whatever subsampling (or none quite possibly) these cameras are using with 8-bit, though the bitrate could be raised as well for faster cards should be no problem, just less than 12 min clips - no prob for film makers.
Possible to also implement a different codec for whatever reason someone could think of