People are saying Mike Haggar (AKA the man with "das pipuh") from Final Fight (and Marvel vs. Capcom). I hope it's not (fingers crossed for Violent Ken) but it seems to be the choice that makes the most sense; 3/4 of the returning characters are from one game: Rolento, Poison, Hugo are all from Final Fight .
Ono and Peter Rosas (combofiend) have comfirmed that this character has not been in a Street Fighter game before, hence Ingrid is not likely unless they were lying or don't count the PSP version - which is completely possible. Capcom is rehashing these characters and the "new" stages from Street Fighter X Tekken; they are literally copying and pasting from there to here albeit with new animations, but not completely new. The new character is probably going to be one from a previous capcom fighting game, but that has never been in Street Fighter.