Yes, I realize only the most devoted network geeks will care about this, but I had to post about it. I don't know what version of iOS this arrived in; I'm running 10.3 beta and I'm on AT&T. I know the feature arrived since iOS 10.0 because 10.0 did NOT support this. But yes, when I tether my laptop through my phone I now get IPv6 addresses on the laptop, and they work! I looked them up; they are unique addresses assigned to each tethered device within the same /64 prefix the phone itself is using. The only downside is these addresses are firewalled for incoming connections; I was unable to SSH to my Macbook over the Internet from another IPv6 connected host. It is nice to see that Apple and AT&T are supporting modern network standards well, though.