Capcom has already teased "new challengers" for Super Street Fighter IV arcade. At a recent location test, it was discovered that Capcom apparently has space for them, too.
Pictured is the character selection screen for the arcade version of the game. There appear to be two blank slots, one on the right and one on the left. The player who took this photo said he was not able to move the cursor over to the slots to see if there were for new characters.
When Capcom brought Street Fighter IV from arcades to the home console, it added new fighters. Adding new characters to differentiate versions is what Capcom does. It's the company's M.O.
If two more characters are coming to Super Street Fighter IV, whoever could they be?
Picture [yfrog via yoshizo715 via Andria Sang]