Quoted from Protodude's Rockman Corner:
the game is called Project X Zone (the 'X' is pronounced as "cross"). The game is a strategy RPG featuring characters from all three companies.
According to the magazine, characters will team up in pairs for fight scenes.
The included characters (from the same post at Protodude's Rockman Corner) are:
Ryu & Ken (Street Fighter Zero), X and Zero (Mega Man), Demitri and Dante (Darkstalkers and Devil May Cry), Chris and Jill (Resident Evil)
Shinguji Sakura and Ogami Ichiro (Sakura Wars), Pai and Akira (Virtua Fighter), Kurt and Riela (Valkyria Chronicles), Ulala and Touma (Space Channel 5 and Shining Force EXA)
Sanger Somvold (Super Robot Wars), Jin and Ling Xiaoyu (Tekken), Kos-Mos and T-elos (Xenosaga), Yuri and Estelle (Tales of Vesperia), Kite and Black Rose (.hack)
Several screenshots can be found here on Famitsu.com for those interested (and an English-translated version via Google Translate here).
Just thought I'd make a post about it in case anyone here might be interested in it, but hadn't heard about it yet.