We got our first look at Gotham Knights on the weekend, following a year of teasing. It's set after the apparent demise of the Caped Crusader and features Batgirl, Nightwing, Robin and Red Hood trying to save the city from the Court of Owls. It is not, however, a continuation of the Arkham series.
That's not particularly clear from the trailer or gameplay slice. Arkham Knight ends by setting this exact scenario up, where the Bat Family has to step in and protect Gotham in Batman's absence. WB Games confirmed that Gotham Knights is set in a different continuity, however, despite the connection.
Expect a whole bunch of similarities, though. WB Montreal also created Arkham Origins, and from the Batgirl sections of the gameplay walkthrough it looks like she plays a lot like Arkham's Batman.
The Arkham series is instead being continued by Suicide Squad: Kill the Justice League, despite it seeming to have a less tangible connection to the universe than Gotham Knights. The cinematic trailer shows the gang—Harley Quinn, Deadshot, Captain Boomerang and King Shark—hanging out in Metropolis, before their fun is interrupted by Superman, who seems to have developed a penchant for murder.
Aside from Harley and Deadshot (who's been redesigned) appearing in the Arkham games, it's not clear how else they'll be connected, or if it even really matters beyond branding. Tonally it seems lighter and more slapstick, and instead of sneaking around in the shadows and terrifying goons, you'll be flying around with jetpacks and causing carnage as a cannon-wielding shark.
Gotham Knights is due out next year, and we'll have to wait until 2022 for Suicide Squad.