First up we have Rufus, which we already know about, but this pic is just funny just because of Ken's facial reaction (the facial expressions strike again!!). The storyline for Rufus is supposedly he is Ken's rival and still beats people up that looks like Ken. Of course there are comparisons of Rufus from Earthquake (Samurai Showdown) to Bob (Tekken 6).
Then we have Seth (likely the final boss of SF4), who I assume is the first versions of Urien and Gill (Street Fighter 3). The storyline for him so far is that he is involved in the weapons division of Bison's Shadoloo business. His only difference to Urien and Gill is the eye thing on his stomach, which is likely fires projectiles (pic below)If he plays like Urien in SF3 3rd Strike, get ready for lots of Aegis Reflectors (his likely normal super), his charge move (pic below), the knee dive, and those projectile shots. I don't want to call out his Ultra yet assuming he can use the Aegis Reflector (high-tier Urien players will like that!!).
Word from the streets say that Fei-Long and Dan are also confirmed for Street Fighter 4, but exclusive to the console versions. If that is true, expect them to be officially announced at Capcom's press event, CAPTIVATE, this week (actually next week when the embargo is up).