I think IPv6 privacy extensions are a bit overrated in their usefulness. What I mean, at least for most residential deployments, is that the first 64 bits (the prefix) is the same no matter what you do with the last 64. Even if the exact IPv6 suffix is randomized your address can still be linked to an account by its suffix. Unless you are a part of a large network suffix randomization won't do much good. And large networks are probably better with DHCPv6 anyway. If only Google implemented DHCPv6 for Android...