In order to predict how bad the long tail will be though we should ideally look at the graphs broken down by network type. Does the increase just represent a switch from people using their residential ISP connection for everything to people using their cell connection more, or does it actually reflect residential connections moving from v4 to v6?
The only way to break the long tail is regulation or forced updates. If you're at 95% rollout, it's fairly likely the last 5% of holdouts won't do it willingly, so they need the stick.
I would definitely support regulation here, especially regulation forcing ISPs to provide v6. That would at least take care of one large part of the problem.