Alternately, Microsoft could step in with the various service layers they developed for Windows Phone.

If they were to open source alternatives to Google's Play Services and give developers a low or no cost app distribution method, I could imagine them doing a lot of business hosting instances of those service layers on Azure.

Developers get lower costs and Microsoft picks up more cloud share.

They already did started that with their Android launcher; Arrow. (https://play.google.com/store/apps/details?id=com.microsoft....)

It'a also why they're updating Windows 10 steadily to support integrating with Android deeply as well.

Not to mention they've working on their Linux subsystem for Windows (WSL), cross-platform services and apps like VSC, buying Github, Xamarin, etc), and also porting/improving macOS apps like Visual Studio and Office on macOS.

Microsoft's cash cow is now their services and why they're turning previous Windows and Office cash cows into subscription services. I suspect they plan to do an overall Microsoft service; get Windows, Office, OneDrive, and Surface for a monthly price.

Which is what I suspect Apple will do as well as Google; all of them will do software+hardware bundle subscription service. Imagine paying 100$ a month to get latest hardware and software all the time.

Definitely would never happen. iCloud is a huge lock in factor to iOS / macOS. Opening that up would be like opening up iMessage, it would allow way too many people to easily leave the Apple ecosystem. iCloud + iMessage are two of the best features of iOS (and that lovely UI + good security)

Well, the idea is opening it up only for an Apple sold AOSP phone. In some way that attracts customers that aren't in their current demographics, but without cannibalizing current customers. But, yes, agree...won't happen.