Capcom's fighting characters have crossed paths with the X-Men, the broader Marvel universe, Tekken, SNK, Namco, and Tatsunoko. Apparently running out of characters to fight, the company appears primed to turn its wrath on itself with a crossover of its own internal fighters.
The US Patent and Trademark Office (USPTO) shows a registered trademark (via CVG) for "Fighters of Capcom." It was registered by the company earlier this month. As always, keep in mind that trademarks are no guarantee of upcoming projects, and the end result could turn out not to be a game at all.
Capcom has tried to blend its fighting properties before, most notably in Capcom Fighting Evolution. That 2004 title blended characters from various Street Fighter games, Darkstalkers, and Red Earth.