It sounds like there may have been some truth to the Black Ops 3: Zombies Chronicles rumors we’d begun to hear a while ago. It also sounds like it will be an altogether new DLC pack for Black Ops 3, albeit the content within it won’t be entirely new.
According to Reddit user DTZcPorter, who appears to have done some due diligence to discover this, Zombies Chronicles will introduce eight new maps to Black Ops 3‘s Zombies mode- but new here is relative. All eight maps will actually be remastered from previous games in the series. Three will be from World at War, four from Black Ops, and one from Black Ops 2.
It also sounds like it will launch on PS4 first, like with all Call of Duty DLC. It is likely it does get a standalone release, owing to ESRB’s rating for it- but that is just speculation on my part specifically.