They would go back to ww2 if everything else fails

Call of duty: Dinosaur hunter!

wont go out with a bang. They will milk it until the bone is dry. At some point they will realize it needs a break (like Guitar Hero) and will end it abruptly. A few years later they will try a CoD comeback thay may or may not be successful.

Mobile game

CoD Crush.

By then it will be a historic game about World War 3..

Set in WWII at the end of it. You are a loan British soldier stuck behind enemy lines without the knowledge the war has all but ended.

No MP, just SP and it's only £15.

Call of Duty: An Electronic Arts game.

Some F2P title with microtransactions like there's no tomorrow.

But I can't see CoD dying. Call of Duty will die the very same day Activision dies. Even then some other publisher might get the rights to the franchise. It's just like the Simpsons, it will be around forever. People bitch about the quality and how everything was better back in the days, but the games will still continue to sell.

As far as I'm concerned, the last CoD is called "black ops 2". Haven't bought one since.

One thing's for sure, if we ever get to that point, it will have DLC till no tomorrow.