I wish ASUS would release a table with all of their WiFi devices that would simply list the device, if it works with AiMesh, AiMesh 2.0 and if not, is it planned in future firmware updates. For example, I need to extend a guest network & have a RP-AC55 just sitting in a drawer. If I knew it was never going get updated to a 386 (AiMesh 2.0) firmware, I would go ahead and buy a RP-AX56.
I would guess they know what can be upgraded & what can't. As long as the device is a couple years old or more, I think most people would understand not adding new features to firmware. It would just be great to know the plan for the devices that are already owned.