Hole punching still exists in the V6 world if you want an app to do P2P from behind stateful V6 firewalls. It requires a three party handshake just like V4 NAT

Hole punching still exists in the V6 world if you want an app to do P2P from behind stateful V6 firewalls. It requires a three party handshake just like V4 NAT traversal. But unlike NAT traversal it nearly always works since there are no symmetric NAT nightmares. V6 should make all this cruft go away but it doesn't.