I would suspect that stateless Auto configuration works on the phones. As long as it was passed along by the routers it would work just fine.
However that being said ARIN is at 0.07% left of IPv4 space as of a few days ago and likely less after this week. Estimates in July the ARIN free pool will be empty and you'll be leasing IPv4 ip's for a lot more and not own your IP's for quite awhile so it is in everyone's interests to push adoption of IPv6. Google's decision to make sure the phones are compatible as much as possible shoots this into the foot.
However Verizon and AT&T and others are not getting more IPv4 ip's so they'll make sure IPv6 works on the phones.