https://wccftech.com/gotham-knights-announced-for-2021-with-co-op-and-batman-is-dead/

After many years of rumors, Gotham Knights, the next game by Warner Bros. Montréal (Batman: Arkham Origins), was announced today at the DC FanDome virtual event. The game will launch next year and feature an optional two-player online co-op.

As mentioned in the title, the entire premise is that Batman is dead and four Gotham Knights (Batgirl, Red Hood, Robin, and Nightwing) have to step in to fill his shoes. In terms of gameplay, it looks like the goal will be to merge the Arkham trilogy with action RPG elements.