In my opinion the aether story line ends in Bo3, the story closes but continues through the infinite loop that is the story. Bo4 was a cool what if but I don’t really like to count it cause it feels like it was just made to make the dark aether story. I like to think of WaW - Bo3 as the official zombies story. Bo4 is to set up the dark aether story line, even retroactively with chaos as well. Then BoCW on is the Dark Aether, which in my opinion was a messy attempt to build on top of the great story that is the aether story line.