Credit to packetlife.net for this one
NAT64 RFCs Published Last Week - Packet Life
RFC 6144 had an interesting note on IPv6 transition...
"Post-Transition Phase (2012 and beyond): characterized by a
preponderance of IPv6-based services and diminishing support for
IPv4-based services.:"
I don't really think you're going to see any major decline in IPv4 for at least another two years. Other than Techies, ISPs and the Government, nobody has really embraced the IPv4 "sky is falling" bandwagon yet. Don't get me wrong...i'm a fan of IPv6, I just don't think that the transition is going to happen as quickly as the guys writing the RFCs do.