IP's address Internet endpoints, not people using them, yet States, prosecutors, and law enforcement regularly try to create the illusion that an IP has anything to do with who uses something.
IPv6 makes that temptation worse. IPv4 forces you to realize IP's can be ambiguous. IPv6, through having more addresses than people on Earth, checks off the Institutional checkbox for "raw material to contribute to a UUID identity scheme". Just look at China's proposals for a more governable international Telecom network, and the intention to use device persistent addressing as a control mechanism becomes obvious.
Where IPv4 creates enough decentralization and localized namespace unscrambling to provide enough friction via statefulness to thwart these types of efforts, I'm not at all confident IPv6 will do the same. I believe it is just what the Doctor ordered for laying the foundation of coupling IP's and net addresses in the minds of the masses to personal identifiers.
Which is not by any stretch the way we want things to go.
