Even if you did move mobile devices to ipv6 I think we can discount a move to ipv4 addresses as there arent enough of them, thats still not going to give mr plod what he wants. Most internet traffic is still ipv4 and the number of sites using ipv6 is still limited hence most traffic would either need dual stack on the phone and still be via ipv4 CGNAT or go through whatever solution the ISP chooses for IPv6 to IPv4 most likely NAT64 which would still result in a limited number of ipv4 addresses being used for thousands of clients.