360 mission modes? if we assume there's 20 per character (like in SSFIV) that gives us 16, which is impossible, but 10 per character is 32 non DLC characters which is far more believable. So far, there are 30 non DLC characters announced, leaving room for 2 more only. Phoenix is semi conformed from the Marvel side, so the other has to be a Capcom character? meaning no Sentinel or taskmaster?
Ouch, that's more GAF-esque speculation that my head can handle.