https://www.gamespot.com/articles/call-of-duty-black-ops-4-may-use-blizzards-battlen/1100-6457252/

Now that Call of Duty: Black Ops 4 is officially confirmed and teased, an intriguing new detail has popped up that could signal Activision's plans. It appears that like Destiny 2, Black Ops 4 may borrow Blizzard's PC distribution platform, Battle.net.

The official Call of Duty Profile site received an update alongside the Black Ops 4 announcement (via Charlie Intel). In the new update, users can link their Battle.net account with their existing Call of Duty account. That would certainly seem to indicate that Call of Duty games on PC, and more particularly Black Ops 4, may be available through Battle.net.