With the announcement that new characters are slated to be added to the US release of Tatsunoko Vs. Capcom, fans have been hopeful to find out who those characters are. Now we may know, but unfortunately I must file this one under speculation. According to COCOROG, a page on Capcom of Japan's new website for Tatsunoko Vs. Capcom: Ultimate All Stars had unused source code which named the new hidden characters to appear: Zero (albeit which series is unknown), Frank (Dead Rising), Yatterman #2 (Yatterman) and Joe the Condor (Gatchaman). Additionally there is Tekkaman Blade, who is actually on the site.
Looking into the site myself, however, I was unable to find this code spoken of. Nevertheless, COCOROG is a long time trusted source of mine. So either COCOROG is simply wrong, or Capcom got wise to their mistake and removed the code. If anyone is up to some investigating though, we'll be happy to hear what you find. Nevertheless, if this information is true it should be confirmed by the time TGS rolls around.
Update: A post on GoNintendo appears to indicate that the source code did in fact used to be on the website. So Zero appearing in TvC seems that much more likely.