The latest leaked news about new Cod BO III regards a new mode called Nightmares. In this mode, Call of Duty: Black Ops III will allow you to have a run through all of the story mode missions but with a twist: every enemy becomes a zombie.
I don't get the point with this being secret so far, since it's easy to understand this represents a plus in terms of Call of Duty: Black Ops III longevity, apart from the almost eternal multiplayer modes.
By the way, Call of Duty: Black Ops III is releasing on November 6. Nightmares is supposed to be a current-gen exclusive, just like the story mode.