This is missing the point mostly, my own sites have supported ipv6 for a going on a decade because it was fun to get it working. But that's a very different thing than supporting only IPv6.
It's best for an ISP to deploy IPv6 and CGNATv4 in parallel, so the NAT only needs to handle traffic for services that don't support IPv6 (e.g. news.ycombinator.com)