If Microsoft extends their Android implementation to provide new features before Android itself does, and these features become popular, then all Microsoft would have to do is start putting out their own "Android" phones to begin eating the market.
WSL, I'll admit, will be trickier to convert. However, they have decades of experience at this so don't put it past them to figure it out.
Given Microsoft is using/embracing Amazon's replacements for "Google Play Services" isn't the threat here more that Amazon might finally extend Android after a decade of trying and failing?
(Whether or not you agree that "Google Play Services" is already that EEE play, the incumbent, seemingly not going anywhere, and Microsoft/Amazon are playing underdog in this game.)
WSL, I'll admit, will be trickier to convert. However, they have decades of experience at this so don't put it past them to figure it out.