I don't think this update really changes anything about the status quo, then, other than the fact that IPv6 seems to have a much higher likelihood of being favored (based on the ratios provided by the poster).
If you had privacy concerns about using IPv6 before, they remain, and (presumably) you can still disable it at a systemwide level.
Personally, if you're sophisticated enough to be using a VPN for privacy purposes, you can probably figure out whether or not your given solution supports IPv6.
In addition, I disagree that IPv6 is some sort of abject reduction in privacy. Many households already have a single member, so IPv4 wasn't providing much cover there. And (speaking from some experience) IP addresses aren't the best resource when doing tracking: that's what evercookies and supercookies are for.
This is actually a huge change for Apple as iOS and OS X would only use IPv6 ~20% of the time because of the IPv4 bias the old algorithm used. After this change, I expect to see IPv6 at the level's we see at facebook with our app to approach 80%, which is a huge improvement and hopefully results in a good rise in IPv6 usage on the internet.
> And (speaking from some experience) IP addresses aren't the best resource when doing tracking:
No, but IP-based tracking is even easier than many other methods and can be done passively.
The IP address may not be the only identifying piece of information, but IPv6 includes strictly more information that can be used to track you, and it makes it far easier to take advantage of that information. Supercookies are bad, but it takes even less tech sophistication and effort to track someone by IP address than with a supercookie.
> Many households already have a single member, so IPv4 wasn't providing much cover there.
A lot of people sit behind NAT with many members. Much as I hate NAT, it does provide this benefit, if only by accident. IPv6 makes it far easier to disambiguate two users behind the same NAT without having to look at any other bits of information (cookies, UA strings, etc.).
IPv6 has privacy extensions. On my home network my computer grabs a new IPv6 address every 30 minutes. Yes it's all out of the same /64, but this provides the same sort of smearing that NAT does.
If you had privacy concerns about using IPv6 before, they remain, and (presumably) you can still disable it at a systemwide level.
Personally, if you're sophisticated enough to be using a VPN for privacy purposes, you can probably figure out whether or not your given solution supports IPv6.
In addition, I disagree that IPv6 is some sort of abject reduction in privacy. Many households already have a single member, so IPv4 wasn't providing much cover there. And (speaking from some experience) IP addresses aren't the best resource when doing tracking: that's what evercookies and supercookies are for.