It's been teased for some time, but now at today's big DC FanDome event, the official trailer has been released for Batman: Gotham Knights, the successor to the Batman: Arkham, albeit it without the participation of Rocksteady who made the initial games a success. Instead, this new game will be handled solely by Warner Bros. Games Montreal (Who solely did Batman: Arkham Origins to keep fans entertained while Rocksteady was working on Arkham Knight).
And interesting thing to note is the new game doesn't seem to be a sequel to Arkham games, although it's jump off point is essentially where Arkham Knight ended with Bruce Wayne dying, destroying the Batcave as a precautionary measure. As a result, Robin, Nightwing, Batgirl, and Red Hood must step up and take over the mantle as they take on the Court of Owls who’ve sinister plans for Gotham. How audiences can tell it isn't a direct sequel is a number of things including redesigns of all the characters, Barbara Gordon still wearing the Batgirl mantle (In the Arkham games, she had already transitioned to Oracle and was crippled), and her father Jim Gordon being dead.
The game seems determined to rather be a more colorful, open gameplay experience, boasting not just a singly player gameplay but co-op (Something the Arkham games never wanted to do for fear it would take gamers out of the experience). The game is expected to be released in 2021. Check out the World Premiere trailer for it below: