Add a fourth company to the group contributing to Project X Zone – Nintendo. At least, it's a Nintendo-owned developer creating the 3DS Capcom/Namco/Sega crossover SRPG. Monolith Soft, most recently known forXenoblade Chronicles, is developing the new game, Famitsu has revealed (viaAndriasang).
It makes sense given Monolith's history – it developed Namco X Capcom, a similar crossover game for PS2. What doesn't make sense, at least at face value, is a Nintendo-owned company making a game about three other companies' characters.