I think the Animal Crossing series will need a complete overhaul next time - just like the Zelda team did with Breath of the Wild.
New Horizons is basically the pinnacle of the concept that started with Doboutsu no Mori that started on the N64 23 years ago.
I don't see how this concept can be refined any further by throwing in more furniture, more villagers, and more of the same. If you think about it, there is no need to go back to previous AC games, because contrary to iterative series (like Zelda), it is basically the same game that's remade with new features, better UI, more furniture, and better graphics. Animal Crossing is like Microsoft Excel : why would you go back to a previous version if the new one does the exact same thing, but better?
The next Animal Crossing game needs a shakedown : scrap the rolling log view, let the player control the camera, make it an expansive world, rethink the core concepts, make interactions with the villagers more meaningful. More of the same is not the way to go. Reinvention served the 3D Zelda series a lot, and I think Animal Crossing will need to go down that road.