Time will tell if they'll release anything like iCloud for Android, at least in terms of something similar to what they did for Windows (not necessarily full device backup), but I think it's more likely now than it was a couple years ago.
Now if they'd just release Messages for Windows I could finally delete Skype.
iMessage will likely never be cross-platform. Apple sees the writing on the wall, only ~10% of their userbase gets the fully integrated iOS/Mac experience, and they know they can't leave the remainder out in the cold wrt accessing their own files (hence iCloud being web accesible).
Yet you won't see Airdrop, proper Time Capsule support or other core features that don't make Apple recurring revenue add support for Windows, Android or Linux. Apple has been selective about what they're willing to do on other platforms, and its whatever they think they need to do to ensure their 1 billion iOS users are somewhat happy, while not letting their Mac sales lag (by letting the moat disappear).
Yeah, this is interesting. I still think my argument about having features as a differentiator still stands - Apple would never build (and Google would never allow) Apple to have a seamless backup and restore solution like iCloud on Android. Maybe they'll build a client, but it's always going to be a second class citizen when compared to the native clients.
It's a brand-new version of the app that uses Microsoft's new APIs, and it probably part of a deal to get OneDrive to better use Apple's own file APIs on the Mac and iOS. Maybe the rest of it is old and sucks but the file sync parts are all new.
Some of the dialog boxes look the exact same, but the underlying storage engine is entirely rewritten with the big change being that files are now stored with the same Windows API that backs OneDrive's "Files on Demand" feature where File Explorer now shows the entire contents of iCloud whether or not it is available offline, and Windows will ask iCloud to download files if you try to use them.
https://support.apple.com/en-us/HT204283
Time will tell if they'll release anything like iCloud for Android, at least in terms of something similar to what they did for Windows (not necessarily full device backup), but I think it's more likely now than it was a couple years ago.
Now if they'd just release Messages for Windows I could finally delete Skype.