I can't see any sign that long-term IPv6 growth has stopped, it's just ceased to accelerate. Looking at Google's IPv6 traffic graph (https://www.google.com/intl/en/ipv6/statistics.html), this is entirely consistent with being the first half of a classic logistic curve, with growth now linear as it approaches the 50% point after 15 years. If this is actually a logistic growth curve, we will presumably see the end of IPv4 sometime around 2040. Even if we take a more optimistic view and assume linear growth continues, it will still take until about 2035.
And that's fine. Old technlogies tend to wither away, not go out with a bang.