Hu? I don't get what you are trying to say ... yes, one usually should have a stateful packetfilter at the uplink, with IPv6 just as with IPv4, with NAT just as without, what is your point?
There is a difference between theory and practice: there is no specific use of stateful firewalls in today's IPv4 mr. nobody home router (i.e. most of the routers do not use the --state option of iptables). If we move to IPv6 only, ISPs need to (and will) use --state (or equivalent). The way mr. nobody has a sort of "stateful firewall" nowadays is actually thanks to the popular use of Masquerading NAT (i.e. iptables -t nat -j MASQUERADE). So jackweirdy is kind of right "NAT" (in practice) as become a pillar of internet security, in spite of itself.
