Not sure of the full details yet, but it looks good - a new comic con trailer for Street Fighter x Tekken shows Poison, Hugo, Cody, Guy, and a glimpse of Metro City's Moustachioed Mayor Mike Haggar right at the start.
AFAIK only Poison is confirmed as a playable character right now - as she's the only one to appear on the game's Japanese site http://www.capcom.co.jp/sfxtk_en/character.html
But I think it must be very promising for the others, it will be awesome if it happens.
Really happy to see Poison make a playable appearance at last. I really like their interpretation of her character design - very foxy, and totally 'working it' but still there's just something about her that makes you wonder. Capcom isn't saying but seems to be tipping a wink on the character's bio too - 'She may look like a finely curved woman, but looks can be deceiving!' (http://www.capcom.co.jp/sfxtk_en/ch_poison.html#main_menu)
I'm not quite sure about the riding whip because I don't think weapons belong in vs fighters but I guess it fits with the kinky style of the character.
As a fan of Final Fight, Street Fighter and Tekken, who had a weird early teenage crush on Poison, I'm very happy right now :)