I'm worried about the long tail. IPv6 won't actually be useful until more or less everything supports v6; as long as there are enough clients which don't support v6 servers need v4, and as long as there are enough servers which don't support v6 clients need v4. And until we can start disabling v4, v6 gives no advantage and only causes significant added complexity.
I'm worried that the time when we can start removing v4 and therefore see the actual advantage of v6 won't be here for at least a hundred years, optimistically.
I'm worried that the time when we can start removing v4 and therefore see the actual advantage of v6 won't be here for at least a hundred years, optimistically.