[typh00n]

What I worry about in a fully adopted IPv6 world, are the old Games that run on IPv4 p2p. (like C&C3)

Sure, you can do a IPv4 VPN with your friends, but that means no more games with strangers over the internet.

[Gormo]

Adoption of IPv6 by large organizations for their services doesn't make IPv4 go away.

And even if ISPs stopped issuing IPv4 addresses to end users, there's nothing stopping anyone from setting up a public VPN into an IPv4-based virtual LAN -- if there was demand for it, it could easily be offered by the same services you're currently using to find "strangers over the internet" right now.