Activision is not confirming anything now, stating, "We don't comment on rumor and speculation". There's no single-player game version of Black Ops 4. A source also said that cooperative modes could be used as a replacement for the lack of a solo campaign.
All sites report that Treyarch will focus on expanding the game's competitive multiplayer and Zombies modes to compensate, and that additional co-op modes may also appear. On the other hand, paid games like Call of Duty offer in-game purchases and DLC packs to earn extra revenue. The reason for this might seem surprising too; rather than choosing to focus exclusively on multiplayer, it seems Treyarch, the developers for this year's entry, didn't have enough time for a single player campaign. I'm honestly a little surprised at any effort by a Call of Duty game to leverage a Battle Royale mode. This is also despite the respective development teams now having three years in which to complete a Call of Duty game.
Who is making Call of Duty: Black Ops 4?
Both the Battlefield and Call of Duty series used to be the kings of online multiplayer gaming, but a shift happened past year thanks to both PUBG and Fortnite. However, thanks to reports by Polygon and Charlie Intel, fans have learned some new information regarding the fourth title in the Black Ops series.
Activision was contacted by the outlet for comment before the report went live. It seems as if the Zombies mode included in the games have been untouched, meaning that a possible solo player option for that mode is still on the table. Luckily, there is an official reveal slated for May 17th so the rumors and reports can finally be laid to rest. This used to be a differentiating factor between the Battlefield series and CoD, and while the quality of the storylines and characters has inevitably varied, Infinity War and Treyarch have usually done a reasonable job of packing at least a few standout missions into each game.
Activision is set to officially announce Call of Duty: Black Ops 4 in mid-May (it's already been teased last month), at which time the publisher will reveal various details about the next CoD installment.