It looks like Warner Bros. Interactive Entertainment didn't just register the domain for the upcoming Suicide Squad game, but also for the next Batman family-themed title, which could be titled Gotham Knights according to this registration. The domain was actually first registered back in 1998, but it was updated on June 14th, only two days before the Suicide Squad one.
According to the DC wiki from Fandom, the title could suggest that the game will be about a team of 'young vigilantes' founded by Batman and Batwoman. It is unknown whether that means the previously rumored focus on the Court of Owls remains in place or not.
Batman: Gotham Knights is a Batman comic book series that ran for 74 issues between 2000 and 2006. It began as a successor to the popular series Batman: Shadow of the Bat, and later concluded with the "Payback" storyline as part of Hush Returns. In-universe, the Gotham Knights or Gotham City Knights is a name used by several sports teams. After DC Rebirth, "Gotham Knights" is the name of a team of young vigilantes formed by Batman and Batwoman.
The most recent rumors hint at Warner Bros. Montréal leading the development of this game. Additionally, its release could be as close as this Fall, which definitely isn't out of the question considering that the studio hasn't managed to release a full game since 2013's Batman: Arkham Origins.
Supposedly, Gotham Knights could be the start of a 'DC Game Universe' followed up 'shortly' by Rocksteady's Suicide Squad and other projects in the works at the two studios. After many years of waiting, fans of Batman and DC as a whole could be about to get several games in a relatively short period of time. We'll keep an eye out on additional leaks and rumors ahead of the official DC FanDome event due later this Summer.