The next big OS is going to be Google Fuchsia, which runs on the Magenta kernel (not Linux) and runs apps built with Flutter.
Inb4 nay-sayers, but if you have followed Fuchsia for a few months and have seen the speed of development and just how many people and new technologies are involved, you will see why this isn't even a question.
Given Google's current track record for AOSP with bringing active development into Google Play and deprecating open source components, I am skeptical that it will be good for openness.
Inb4 nay-sayers, but if you have followed Fuchsia for a few months and have seen the speed of development and just how many people and new technologies are involved, you will see why this isn't even a question.