On the bottom of the press release Capcom released about the game you can see them mention Resident Evil and Devil May Cry, two series that weren't represented in the Japanese release of Tatsunoko vs Capcom, so I'd expect a character from each of those franchises to appear in TvC. It may mean nothing though.
Just for reference, the copyright junk on the bottom of the original press release:
"Capcom, the Capcom logo, Resident Evil, Mega Man, Darkstalkers and Devil May Cry are either registered trademarks or trademarks of Capcom Co., Ltd., in the U.S. or other countries. Street Fighter is a registered trademark of Capcom U.S.A., Inc. Gatchaman is a registered trademark of TATSUNOKO PRODUCTION CO., LTD. “Tatsunoko VS Capcom” is developed and published by Capcom Co., Ltd., partially licensed by TATSUNOKO PRODUCTION CO., LTD. Wii and the Wii logo are trademarks of Nintendo. © 2006 Nintendo. All other trademarks are owned by their respective owners."