Note that this is measuring clients of Google services. It's useful for tracking consumer ISPs, but applications that really benefit from e2e connectivity have been and will be moving faster.
looks like another 10 years at most going by the current rate. And I expect it will speed up at the end when we reach something like 90% and some sites go v6 only.
https://blog.apnic.net/2021/02/08/ipv6-in-2020/