Comcast does IPv6 (in most areas, at least), AT&T does IPv6 (was 6rd when I was a customer), CenturyLink (or whatever they're called today) had 6rd on DSL when I was a customer... and it made their CPE do terrible things so it needed to be disabled, but it was offered. My muni fiber ISP offers IPv6.

> At this point it would be best to recognize the sunk cost and give up on the migration. IPv6 will never reach the 100% needed to turn off IPv4.

That was probably a reasonable take 15 years ago. But we're at 50% v6 globally, and the ISPs that are doing v6 + cgnat would not want to move all that v6 traffic to cgnat. v6 traffic is managed with stateless routing; cgnat is stateful and costly.

There are many lessons that can be learned, but v4 only is not the future. v6 only might never happen... people are going to keep running old software in emulation that will never support v6... But global routability of v4 will likely end one day. And I'd suspect the tail of the migration will be much shorter than the head was.