1. Consumer grade routing hardware that always supports ipv6 out of the box.
2. ISPs transitioning into supplying both an ipv4 and ipv6 address to households.
3. Major network backbone services (google, amazon, etc) transition to both ipv4 and ipv6.
4. Once a majority of the critical network infrastructure is available on both, ISPs need to start dropping ipv4 addresses from customers, preferrably from new customers.
5. Slowly depreciate ipv4 by using a ISP provided ipv4 tunnel service for a while for those that still need to access the ipv4 web.
Basically, it requires most of the work be done on the backs of ISPs. In the US at least, the ISP business is an oligopoly of cable tv and Hollywood and will resist ipv6 because it enables more peer to peer trafficking and open communication over the Internet.