I actually hope this the last Arkham game. As much as I adore this franchise, I really think it got milked with all the tie-in comics, filler game/DLC's, the upcoming film, etc. It's something that started a couple of months after Arkham City was released.
I'm only speaking for myself here, but I never needed an "Arkhamverse". What I loved about the first two games is how ambiguous they were in terms of their location. They felt as if they could take place in regular DC continuity; just another two Batman adventures in the Batman canon as we know it. Maybe they were in their own universe, maybe they weren't. Maybe all events from the DCU took place, maybe only some of them did, maybe none of them did. Now we know how certain things in this universe came to be, how certain things outside of the games in general came to be, etc.
I'm not saying that's a bad thing narrative-wise, but I much preferred the original ambiguity Rocksteady was originally going for. Especially since the Arkhamverse always felt too straight-off-the-page to need all of this. If they would've done this with a universe that felt and was more different to begin with though, such as the Nolanverse, that would have made a bit more sense. Just my opinion.