Sonic 4 likely coming to PC. Set your disappointment levels to mediocre.
According to a perusal of Sonic Retro, some Steam registry investimigating has turned up that since being first put on Steam, it's been heavily updated and looks to have a configuration menu outside of the game, like Sonic Generations.
...this physics demonstration highlights one of the reasons why it wasn't as loved by the fan-base as it intended to be.
On the plus side, maybe it'll be moddable? Ironic that Sonic 4 was intended to be liked by the 'hard core' fans, whilst Sonic Colours wasn't and how the two groups seemed to like the other game more, generally speaking. Which begs the question, why the hell haven't Sega realised they'd get a good load of sales off a well priced Sonic Colours port to PS360/PC?
In other Sonic related news, no word on the release date of Sonic Generations' DLC (Casino Night pinball) which was supposed to be released Boxing Day, as well as absolute silence on the Sonic CD front. That, too, is in the Steam registry but seems to be kept quite quiet.