He suggests your identity data be stored in the cloud so all your browsers and devices can access it.

He doesn't mention whether or not you need a password to connect your new phone to your cloud identity wallet...

I didn't sense that he meant for the user to be involved in the cloud aspect, just that the browser stores it there so that it can persist beyond sessions, single computers, etc.

If the goal is no more passwords, what is the handshake mechanism to move my Firefox data to Opera?

Given this, what he describes isn't that different than using something like LastPass, letting it generate random passwords for you, and accessing your login info from multiple devices with it.