I think this is different. They're talking about using a new IPv6 for
each connection. RFC4941 just changes it over time IIRC. IMHO that's
still pretty good privacy, at least on par with a NATed IPv4 from the
outside perspective, especially if you rotated through temporary IPv6s
fairly frequently.
Of course, for browsers, as someone else mentioned, it's somewhat moot
because of cookies.