From Kotaku.com:

Those aren't two interpretations of the same piece of news; if Game Informer are to be believed, then two fighting games are currently in development, both pitting the stars of Namco against the stars of Capcom.

Note these are fighting games, not a continuation of the old Namco x Cappcom RPG title that appeared on the previous hardware generation. Why two games? Simple: each company makes one! Capcom would be developing Capcom vs Namco, built on the Street Fighter IV engine, while Namco will develop Namco vs Capcom, which will run on the Tekken 6 engine.

As fighting game fans are already no doubt coming to grips with, this would mean two significantly different games, Street Fighter IV's 2D arenas contrasted nicely with Tekken's more three-dimensional combat.

GI say that Street Fighter IV producer Yoshinori Ono is handling Capcom's side of the deal, while it's expected Namco Bandai's Katsuhiro Harada will be in charge of the opposing project.

If this information is good - and there have certainly been strong hints to suggest it is - then the two games' debut trailers will be shown this weekend at the San Diego Comic-Con.