I have no idea what it is. But if Banpresto (of super robot taisen fame) developed this, i am sure that this will turn into some kind of epic crossover game. I imagined it would look like Namco X Capcom, but with additional SEGA characters to make it more crowded and epic :3
Great, now i almost wishing it would include Tails X Klonoa multiple assault, or Yuri X Jade and Carol (in Klonoa Costume) X Klonoa, then Arthur X Dante will obliterates all devil XD
Well, that's all just a fan speculation. Let's just wait patiently and hopes it won't be dropped like that case with Megaman Legends 3.'