Zombies really needs to be it's own platform. It needs to be it's own game because let's face it, sure multiplayer is good but the only reason people play treyarch's games are because of ZOMBIES! Imagine it Call of Duty Zombies, it's own francise away from campaign and mp. So this could leave room for lot's of possibilities like a main campaign/Main story of zombies then you could have survival where you just play for getting high rounds, co-op where you play with friends for fun,grief and turned and treyarch can add all kinds of fun like a 12 player infected mode like on MW3 but instead of turning into humans they play as a zombie to try and eliminate other players!
Also i am doing a zombies clan so if you want to check it out it's called the BornForFighting clan and message Richtofenz BFF for a tryout!