If your protocol is that rapidly changing, you shouldn't be launching anything to the public, period. Especially if you're replacing an existing service with it.
If it wasn't being used by the public, then the protocol wouldn't be rapidly changing. Internal use, even by a company as large as Google doesn't give enough variety of circumstance and use-case to drive the changes.
Why not?
Because as soon as you release the spec, people will start building stuff against. This creates resistance to changing the protocol.