It looks like Namco just released info on a new RPG on the 3DS that has characters from Capcom and Sega as well! Seems like an updated Namco X Capcom, but with Sega. You can have up to 5 playable characters on screen at a time! Here are the characters confirmed so far:
NAMCO BANDAI
Sanger Somvold (Super Robot Wars), Jin and Ling Xiaoyu (Tekken), Kos-Mos and T-elos (Xenosaga), Yurie, Estelle and Flynn (Tales of Vesperia), Kite and Black Rose (.hack), Haken Browning and Kaguya Nanbu (SRW Endless Frontier), Valkyrie (Legend of Valkyrie), Alisa and Soma. (Gods Eater Burst)
CAPCOM
Ryu, Ken and Chun-Li (Street Fighter), Mega Man X and Zero (Mega Man), Demitri Maximoff, Hsien-Ko/Lei-Lei and Morrigan (Darkstalkers), Dante (Devil May Cry), Chris and Jill (Resident Evil), Arthur (Ghosts N Goblins), Frank West (Dead Rising), Princess Devilotte de Deathsatan IX (Cyberbots)
SEGA
Sakura Shinguuji, Ichirou Oogami, Erica Fontaine and Gemini Sunrise (Sakura Wars), Akira Yuki and Pai Chan (Virtua Fighter), Kurt Irving, Riela Marceris and Imca (Valkyria Chronicles), Ulala (Space Channel 5), Touma and Cyrille (Shining Force EXA), Zephyr and Leanne (Resonance of Fate), Bruno Dillinger/John McClane (Dynamite Cop/Die Hard Arcade), Rikiya Busujima (Zombie Revenge/House of the Dead)
ORIGINAL
Kogoro Tenzia and Mii Kouryuuji
For more information, here's the trailer: