The US is at 8% IPv6, I think that's enough of a base of early adopters that I could believe as soon as there was some actual pain involved with v4 we'd see some fast changeover.

In other words, I believe the limiting factor on v6 adoption is no longer technical or interop, instead it's lack of problems with v4.

I have an IPv6 enabled home internet connection, and can connect to IPv6 enabled websites with it, and there's no 6-to-4 conversion or having an OS level tunnel to Hurricane Electric.