Yeah Treyarch could go so far with zombies as its own game cause they would not be limited to save room for multiplayer and solo campaign. Including reserved dlc for MP, I think multiplayer is fine and i play it sometimes but that should only be along side with solo campaign. Yes it started out as a little add-on gamemode but its getting really big so in about 2 years after Black ops 2 is released, they should extend their zombies devleloper's team and almost branch out of Call of Duty but I mean as only zombies as the whole game.
I'm not sure if black ops 2 will have its own campaign cause with all the easter eggs for the hidden storyline, but it would be awesome for zombies to be its own game for example (Call of Duty: Zombies).
This could have its own actual campaign up to 4 players, litterly 100 gamemodes (at least) and maybe even a TDM where there are 8-10 players as humans vs zombies and you would try to get the most points like you would normally within a time limit cause otherwise humans would always win but these zombies would be really hard to kill, the zombies could have their own killstreaks but could be called mutators so they turn into a screamer or napalm plus which ever other crazy zombie you could think of!
I dont think that TDM should be humans vs zombies (played by humans with AI's) cause that would be too much like L4D which is not what we want. I dont think we should be zombies at all, as much as cool it would be, it wouldnt be like Call of Duty's Zombies. I thought of a gamemode where we could be zombies and have a objective to stop humans for something but zombies dont have objectives and it would be like Dead Space 2 so no.
But the ideas are really endless cause thats all that there would be on the disc, Zombies!