Could be 95% of all traffic, or 95% of all websites, or another similar statistic. I'll accept any metric that seems reasonably describable as "95% of the internet uses IPv6". If at least one such metric crosses 95% and I trust that it's accurate, this resolves YES.
(Simply supporting IPv6 is not sufficient, it needs to be used.)
here's a graph: https://www.google.com/intl/en/ipv6/statistics.html . It has a weirdly periodic pattern where IPv6 adoption peaks on Wednesdays and is lowest on the weekends (although some years it's the reverse!), and I have no idea why. But if you just eyeball the data, it seems to be sigmoidal, so since adoption hit 5% around 2015, and should hit 50% around 2026-ish, then sigmoidal extrapolation suggests that adoption should hit 95% around 2037, assuming it'll flatten out at 100%.