It might just be a pipe dream, but I really hope they put saved films feature in at a system level. Ever since Halo 3, I've been dreaming of such a thing built into the guide, so it could be executed at anytime within any game, and then shared with friends. It would only be viewable if the other party had the game running, of course, or perhaps also allow a live video stream, from the player who saved the film (if they're currently playing said game) to someone else who's viewing in a theater mode built into the dash (perhaps even a screen sharing feature).
I'm not sure if this would be possible, given the way Halo (and CoD BO?) does it is (the whole saving the game data thing, instead of actually recording video), but it would be really cool if they could pull it off, and would probably also make for one hell of a word-of-mouth marketing tool. Perhaps even more beneficial to games marketing than demos, given the argument that demos do more harm than good for a lot of games.
Not that I have much interest in marketing. I just think that MS (or Sony or Nintendo) might see it as a cool feature that also brings some value to the table.