If you've been waiting for a PC version of Super Street Fighter 4, it's not going to happen for a bit, if at all. According to Yoshinori Ono, the series producer, piracy rates were so high on Street Fighter 4, the PC version won't be released until some robust piracy protection device can be found. So blame the software pirates for this one.
To add insult to injury, according to Ono, the game is technically "99 percent ready" to be released on PC as it is, but Ono and company can't afford to essentially give away the new game, so no PC release is forthcoming. There won't be a Steam-only release either, as Ono feels it would be unfair to people unable to play the game through Steam.
Pirates are incredibly resourceful and clever when it comes to defeating copy-protection schemes, so I wouldn't hold my breath waiting for a solution to be found, but still, Street Fighter 4 was a very strong selling title in spite of its reportedly widespread pirating, so I wonder why a PC release wouldn't make sense, even given the actions of miscreant PC pirates.
Source: Andria Sang