I think we'll get Pie before 8.1, Google ADT-2 will launch with it and HW is basically Mi Box
The experience with android tv 8.1 is basically the same (still pretty bugged). We need to wait for the start of next year when Google releases with amlogic new firmware for android tv 9.0 for the S905X, maybe then we can hope in a stable experience.
It looks like that they abandoned Mi Box. It is stuck with bugged 8.0 for forseeable future. Never going to buy a device from this firm. Lastest Oreo has same hard bugs as the other ones. Beta build 2179 is the most usable build to date, if you want your box to be as functional as possible flash 2179 file and hard reset your box.