Guys Arkham Knight is 5 years old. What are you spoiler tagging for its waay past the "protected threshold".
We dont know how much time has passed between Knight and Knights. It mentions the entire police force has become corrupted.
Gordon could have been killed (assuming its true) sometime after Knight which results in that.
I don't know where the idea that it's ok to spoil people if they haven't learned something within a certain amount of time comes from, but don't do it here please. Because it's not difficult to use spoiler tags to prevent people from getting spoiled.
But the idea that the major plot twist at the end of Arkham Knight was developed off screen during a time skip seems like a pretty unlikely way to write a continuation of a story, and they may as well just make a new one at that point.
There's also the fact that in Arkham Knight, Barara
so that would again be another major plot point (on top of Gordon and Bruce) that would have had to happen during a time skip. So this looks unlikely to be a continuation of that story imo.