Google's failure on xmpp wasn't because other players weren't open enough.
It was because they didn't play dirty.

From my "normal-friends", almost no one uses gtalk
Their transition was hotmail -> facebook. Some don't even check their email anymore.
Most of them don't have google accounts configured on their androids

Google use a imessage-watsapp approach.

Make dirty easy unverified Google accounts on first phone boot:
Require Only: Alias, Name, Mobile number, password, EULA.
Second page, with Synchronization options all enabled by default.
All the other information could be added in other moment.

Then send a confirmation sms, with an activation link.

Then synchronize gcontacts by phone number.

Even if they don't know that gtalk exists in their phone, some of their contacts will talk to them through it. Eventually they will realize of its existence.

By the way... I don't think google will really pull the plug from xmpp... Today I can still federate from gtalk, and send invitations to gtalk users from outside networks.