At what share of deployment would you consider v6 as happening — 10%? 20%? 40%? 60%? 80%? 90? Or would you require even more than 100% of the people who have v4 access?
Anyway, given the number of people who have effectively no choice in home connections, what are we going to do when the incumbent provides us with IPv6 only? LTE or Satellite is going to be even less likely to give me a real IPv4 address.