Element 115 is gone and purged from existence. The kids are entering the perfect world. This light leads them to the world where there are no zombies, the element 115 doesn't exist, Primis doesn't exist, Ultimis doesn't exist, nobody, or nothing exists in this arc, everyone is classified as dead.

Call of Duty Black Ops 4 Woods and Mason Ending\n\n The ending in question shows a conversation between Woods and Mason. Woods tells Mason It was you in the box, it always was , he also mentions Angola (which gives a clue as to the event he's referring to), then utters something about her sister .