IPv6 is the brand new addressing scheme for the Internet that will solve all the problems of running out of addresses that IPv4 will run into... um... yesterday. It will provide enough unique addresses to assign one to approximately every molecule of matter on the planet, or at least all the Internet of Things things that Scotty Cowling listed in HRN 289. And by brand new of course we mean 20 years old. And in Internet years, that's old.
We learn all this from Bryan Fields W9CR at the 2016 ARRL & TAPR DCC in St. Petersburg FL. Bryan was a local host for this DCC. He's made presentations the 2015 and 2016 Hamvention® TAPR forums.
And as Bryan explains, this topic affects Amateur Radio in a couple of ways. One is the HamWAN project, a wide-coverage, high-speed data network on 5 GHz. Bryan runs the system in Tampa, and it uses IPv6 addressing. The other is that ham radio has one of the few remaining large blocks of unused IPv4 addresses. And they're worth some money (real money).