Activision's official press release states:
"Call of Duty: Black Ops 4 features gritty, grounded, combat, along with new levels of customization and tactical gameplay, and a variety of new weaponry, maps and modes for the ultimate Black Ops multiplayer experience. The game features the return of the iconic Pick 10 system, along with a series of innovations in weapon controls, combat flow, health regeneration, and player movement. Black Ops 4 goes deeper than ever before into the fiction of multiplayer, where players will explore the world of Specialists – who they are, why they exist, and what battles they fight together – while mastering their gameplay through solo and multiplayer combat experiences. Black Ops 4 features a combination of new and returning Specialists, each with their own unique weapons, equipment and playstyles. Players will be powerful alone, but devastating as a team working together."
Call of Duty: Black Ops 4 will include no traditional singleplayer campaign. Instead the developers have focused on a 5v5 tight multiplayer mode, an expansive zombies mode, and an all new 'battle royale' mode called "Black Out".