Capcom Community Manager, Seth Killian, has said that Street Fighter IV isn't just selling well in Japan, it has sold out.The numbers being quoted some places are off based on what I've been told, but the real story is that SFIV is not "selling well" but is in fact SOLD OUT in Japan.
There ARE no more copies to sell on the store shelves. I heard from Ono-san himself last night that Capcom has a few boxes left in the basement that they'll be sending out on Monday, but they were totally overwhelmed by the demand. Sales couldn't have been any higher because every single copy in the stores has been sold (!!!).
Should be interesting to see how this stacks up with the American release of the game.
There's rumors that stores may be selling the game a day or so early over here, if these turn out to be anything more than rumors we'll have the latest news posted here.