Have you ever watched a movie or a show that had two sides to the story. Well this is what I believe is going to happen.

On one side of the blown up world (in the zombies menu) we have green run. Now in green run there may not be much but it's a place where maxis and/or Richthofen can hornist enough power for whatever master plan they have.

On the other side of the world we have some classified place we don't know of yet but what I think is, that's where the old characters are and they are probably setting up some revenge scheme for Richthofen and/or maxis.

So if you have watched a movie or show like that you would know that they showed on of the story and then the other side. I.e. you play as the new characters in tranzit trying to help Richthofen and/or maxis. And then you play as the old characters.

I will end this post with one last little theory. I also believe that beings how Samantha (in Richthofen's body) know more about the zombies than any one else. That we the players of the game will probably be following her.