I think fans have often requested a co-op game, this might be an answer to that request. Of course, not all fans want such a thing. I certainly hope I could be able to play this by myself in some fashion. If this is just a $10 side-project, just let it be what it is and I'm sure they'll get around to making a full game when the time is right. If its "too" big a thing, it risks overshadowing Lords of Shadow.
This falls in line with what Nagumo was talking about earlier, so I'm going to guess its legit. Man, I love this time when you don't have much to go on but a few pics and some speculation. I wonder what arsenal each character would use. Certainly not the entire arsenal from their games... Wonder if they just give all characters a standard set of weapons, and that's that, or if you can earn new ones throughout the game somehow.