Of course not. Treyarch knows that zombies are the money maker so they will not eliminate it. It will get crazier and crazier, but the only way it will end is if Call Of Duty goes back to Infinity Ward.
As for the storyline, there has always been one. Since Der Reise as far as I know. Its actually a pretty complicated storyline as well. Richtofen betraying Maxis, Samantha getting trapped in the Aether, but retaining control of the zombies, Richtofen switching bodies with Samantha to gain power over the zombies, its a long and well thought story.