Super Strip Fighter 4 update:
Four of the original characters (Yuki, Martha, Amanda, and Nina) are confirmed to be back. I suspect all of the original characters will return based on some of the screenshots.
Four new characters are also confirmed. Ran and Mari from my last post, plus Iku and Jin Tendoh. You may remember Iku from the trailer a few weeks ago. Jin Tendoh is a male character who looks like some kind of crazed otaku. If S returns, that means this game will have at least 2 male characters.
Looking at the character selection screen screenshots, there may be 4 new characters yet to be revealed, for a total of 16 characters.
The homepage also has been updated to explain some of the game system, but I can't read it. There seems to be a "Strip" meter that gradually fills, presumably allowing you to strip your opponent. Each character can pick one of two "Strip Combo"s at character selection, but I have no idea what this does.