Teksavvy, ontario, DSL
Dual stack. Have been since I subscribed. I actually can iPV6 VPN to work from here. Although I did immediately get a call from my buddy in the security team. They didn't like that because... they had no throttling on the IPV6 connections into the VPN.
As for 6 to 4 or 4 to 6. There are a couple of different ways this can be handled, including one particularly interesting suggestion -> to allocate an IPV6 block to be the gateway to IPV4, and to have any device that had IPV6 only on one side and both stacks on the other side effectively become a NAT. DNS lookup on IPV6 only device bolts in the predicate IPV6 block on any ipv4 only return. Going 4 to 6 is somewhat harder, but there are implementations that work, although in the cases I've seen they are effectively reverse proxies.