The rating lists the number of selectable characters as 26, three of which still havent been revealed

After much speculation, it appears we now know the final count of the character roster available in the upcoming western version of Tatsunoko vs. Capcom for Wii. The game has been rated by the ESRB for its US release, with their description mentioning that "players can select from among 26 characters" in the game.

The original Japanese version contained 22 characters, and all bar one—Hakushon Daimaō from The Genie Family, who was removed for licensing reasons—made it into the new release. This means we have five new characters all up, including the already announced Frank West (Dead Rising) and Tekkaman Blade. This makes 12 characters from Capcom and 11 from Tatsunoko, leaving three still unannounced.

However, the recent Capcom site leak could account for these. Based on the file names, it is highly suspected that Joe the Condor (Eagle Riders), Mega Man Zero, and Yatterman #2 (Ai-chan from Yatterman) will be filling these holes. This would mean a character roster of 13 for each of the companies.

Source: ESRB