You actually bring up a good point. v6 genuinely helps here. It gives every device a routable address, so no nat, but it doesn't open a hole through the firewall, which still defaults to blocking inbound, and it doesn't address authentication. You'd still need something to introduce the peers and verify identity. What v6 changes is that hole punching gets easier and more connections go direct. v6 does kill CGNAT specifically, which is the worst case for hole punching. I would really like to see CGNAT go away, which would happen in a 100% ipv6 world. Weirdly, v6 still isn't close to 100%... v6 good for BitBang and doesn't replace, which I assume was the point you were making.