I have the same understanding here. It allows those who switch to IPv6 easily communicate with IPv4 (backward compatibility?)...a bit confusing though since this is handled at router level.

We had a strange case recently...some of our remote staff were unable to connect to our NY VPN from SC. After tracing we found their ISP started using IPV6. Anyways, after we made changes...within a few hours the isp went back to IPv4.

Edit - 19 years to switch is a long time...old as the modern internet. Don't fix it if it ain't broken :)