I've mentioned this previously. Without government-mandated standards, implementation could take years. We apply this approach to numerous areas; why should IP be an exception?
IPv6 adoption will take place overnight when either google chrome, Android or iOS start showing a warning on IPv4-only networks. ISPs and tech companies will start to get flooded with support calls asking about it and will choose to roll out IPv6 to make the problem go away.
Chrome forced the web to go 100% https, the same thing will happen eventually with IPv6.