Re: failed, not
"Please explain. The IPv6 network is already a great deal larger than IPv4 was 20 years ago, and is growing daily"
If that's your measure of success then great. But it wouldn't be mine. v6 has roughly double the number of hosts that v4 had 20 years ago but it's still 0.2% of the Internet, and most of those will be dual stack.
So v6 can continue to grow at that rate and it will take 10,000 years to displace v4, assuming v4 doesn't grow too.
I call that a failure.