It appears there's been a small leak concerning the new characters in Tatsunoko vs. Capcom: Ultimate All Stars. Scrummaging through the HTML source code on the official TvC website, a member of the Shoryuken forums was able to identify file names that correlate with five new fighters, one of which being Zero.
The file names are as follows:
Translation: Zero, Frank West (Dead Rising), Joe Asakura (Gatchaman), Yatterman #2 (Yatterman) and Tekkaman Blade (confirmed by Famitsu).
Seems plausible enough. Of course, don't expect any confirmation from Capcom until TGS; the new fighters are expected to be officially revealed at the show.