I generally agree, but I wonder how popular cloning wallets between devices
will be in future. Right now if someone wants to have a wallet shared
between Hive, blockchain.info and Bitcoin Wallet for Android, we just tell
them they're out of luck and they need to pick one, or split their funds up
manually.

But probably a lot of people would like to use different UI's to access the
same wallets. Sharing key trees is a part of that, though full blown wallet
metadata sync would also be needed.

So I guess we're going to end up with some kind of fairly complex
compatibility matrix. But I agree it may be unavoidable.