If they make it Android-based but Open Source, similar to how the Unreal Engine contains proprietary components while remaining easy to customize, that could be quite the popular move for grabbing market share from Apple and Google.
I, at least, am unhappy with Apple's greedy behavior and also unhappy with Google's Data Kranken tendencies. So there's at least a niche market opening for a 3rd OS. And I'm not holding my breath for Linux. Instead, I think it'll be something like Lineage OS and its privacy protections but more professionally managed.