https://www.pcgamer.com/call-of-duty-black-ops-campaigns-could-come-back/

Treyarch confirmed last week that Call of Duty: Black Ops 4 will not have a single-player campaign, a decision studio co-boss Dan Bunting discussed in greater depth over the weekend. Simply put, the vast majority of players are into the Black Ops games for multiplayer and zombies, and don't particularly care about the campaign, so that's what Treyarch decided to focus on. But that doesn't mean campaigns are definitely gone forever. 

"[The single player mode] is only missing at this moment in time," senior producer Yale Miller told Daily Star. "I really think with every game we make, we finish that title and then we ask, 'What is it fans are gonna love the most?' If that’s another traditional campaign, then we’ll make another traditional campaign."