As I briefly mentioned earlier, Street Fighter IV producer Yoshinori Ono confirmed that the console versions of the title would contain additional content. Among the extras included would be more detailed story information, delivered in the form of in-game engine cut-scenes and fully produced animated prologues and endings for each character.
Capcom were nice enough to show us Ryu's intro at CAPTIVATE last week, and if all of the intros and endings are this well produced, then we definitely have a reason to finish the game with all of the game's characters. The clip cut between a young Ryu watching his master (presumably) in battle with Akuma, and a more mature Ryu going head-to-head with the black-robed devil. Ken, as well as an unnamed grey-haired man, make an appearance towards the end of the clip.
I'm not up to date on my Street Fighter mythology, and despite the clip being fully voiced in Japanese (with English sub-titles), I'm not entirely sure what was going on. But like the title of this post says, it was "mega sweet." Hopefully Capcom will be nice enough to release the clip for public consumption in the near future.
In the meantime, drool over the images, and speculate away.