[UPDATE: WB Games Montreal has confirmed that Gotham Knights takes place in a different continuity outside the Arkhamverse, with something else causing Batman's supposed death. As such, the following analysis is much less likely now. Original Story Follows.]
Prior to the official reveal of Gotham Knights, one of the biggest debates in the community was its direction. Many hoped for a reboot of sorts, as Arkham Knight ends with the death of Bruce Wayne. Instead, Gotham Knights appears to be following similar events, seeing Red Hood, Batgirl, Robin, and Nightwing take up the Dark Knight's mantle after his death.
But this itself poses a ton of questions surrounding Bruce Wayne's successors. Perhaps the most important, though, remains: who appears in Arkham Knight's secret ending?
Arkham Knight's Secret Ending
Players who earn a 100% completion of Arkham Knight see a new, meaner version of the Dark Knight descend upon some ne'er-do-wells. This version seems far more violent, has access to Scarecrow's fear gas, and has a red insignia, leaving many to wonder for quite some time who is and what he is doing. There have been plenty of theories, ranging from Bruce Wayne surviving the blast but changing to a brand new Batman.
After all, looking at the figure in Arkham Knight all but guarantees it's not one of the Gotham Knights. It's not Batgirl, it's not Red Hood, it's not Robin, and it's not Nightwing. This may poke holes in several theories, but there's also a good chance that fans finally get their answer in Gotham Knights, even if it's not an actual sequel.
Gotham Knights - Villains, Potential Explanations
This is obviously speculation, but Gotham Knights could explain this in a variety of ways and, in as many, has to. The seemingly most clean-cut answer would be that it relates to the Court of Owls. As the (likely) primary antagonists of the game, the Court could have something to do with this new Batman-like character, whether it has somehow used its Talon technologies in new ways to bring back Bruce Wayne, whether its Owlman whose costume has become more like Batman's, or whether it's some engineering by the Court not yet identifiable. The former could be theoretically possible, if unlikely, and that's not to mention that fighting a deceased Batman as his proteges would tread seriously dangerous waters for the fanbase.
Owlman, another Talon, or one of the Court's schemes all seem plausible as well, but specifics would be hard to determine. There's also the Batman Beyond teases that could somehow manifest in this character, if the game is willing or even could bring Terry McGinnis into the fold. Another possibility is that it's another Batman-esque character unrelated to the Court that's currently being kept secret, whether it's intended as a good guy or villain, but with a 2021 release date, fans shouldn't expect answers to these questions soon. And of course, WB Games Montreal will likely protect this secret until release, with there a ton of possibilities that go unmentioned here.
What seems unavoidable is this scene being addressed, though. Fans want answers, and as the Gotham Knights rise to protect Gotham City, it seems they may just get them.
Gotham Knights releases sometime in 2021.