Call of Duty: Black Ops 4 was revealed today in a teaser trailer on the Call of Duty YouTube channel. The teaser shows what you would expect, and informs us that there will be a "community reveal event" on May 17th, and the Global Launch of October 12th. Also shown is the games slogan of "Forget what you know." Based on the trailer there is a nuclear threat, zombies, cinematic events, and plenty of shooting. So I would say "what you know" is a pretty safe bet on what Black Ops 4 will be.