Oooh, I think that's really big. That basically forces every app company to make sure their main domain at least has an AAAA record that goes somewhere.
I think Apple could force IPv6 adoption alone by extending this policy... An iPhone update could change the behaviour to only connect to a new wifi network if there is working ipv6 connectivity. "new" would be defined as any network whose mac address is not currently in Apples geolocation database.
That would mean anyone getting a new broadband connection or router would see it as not working unless it had IPv6.
Perhaps you can have an override - eg. "Use this legacy network anyway this time (some apps may not work properly)".