> Adoption will slow down and my guess is that we'll be stuck with a long tail forever, and only time will tell if that happens at 50% adoption or 90% adoption.
But that long tail will probably look like figure 4 of that link, only reversed: IPv4 running mostly as tunnels over a core IPv6 network. Some large cellphone networks are already at that stage, using things like 464XLAT to run IPv4 with NAT over an IPv6 network.
I'm not talking about a long tail of systems and networks which still have working IPv4 support. I'm talking about a long tail of systems and networks which still don't have working IPv6 support.
But that long tail will probably look like figure 4 of that link, only reversed: IPv4 running mostly as tunnels over a core IPv6 network. Some large cellphone networks are already at that stage, using things like 464XLAT to run IPv4 with NAT over an IPv6 network.