Yes it is planned and will be implemented when there is a library for the development system which I'm using for Android. You can use the official Microsoft OneDrive app to upload and download your logbook file from the "Diving Log" folder on Android to the "Divelog" folder in OneDrive.
Just make sure to close the Diving Log Android app from the app menu before syncing with the OneDrive app:
Yes, that would be possible if no library will show up. I try to avoid that because it's a lot more work and adding download support to the Android app has a higher priority for now, but I will use the REST API if there is no solution available in the future.
Sadly, my spare/business phone is now an android (what a pain to use) and I just purchased your app for it. Will still be using my Windows Phone as much as possible.