Unseen64.net broke the story that back in 2006 Backbone Entertainment pitched a concept game to Capcom called Street Fighter IV Flashback. The game was supposed to be a 3D 1-on-1 fighter powered by the Unreal 3 engine.

It never went beyond the concept stage, but this piece has several bits of art they used to pitch the idea including 3D models and some information on what the game play would have been like.

Worth checking out.