But whether you internetwork with IPv6 and NAT, or just keep IPv4, NAT will not go likely go away. The "math" below works out because 9 billion people don't each need a unique IP address. The vast majority of those people will be serviced via NAT, as cable and dsl providers are starting to do now. Whether this is replaced by IPv6 inter-networks sooner or later is probably irrelevant to the kinds of services offered to the people behind the NATs. The problem of course, is that once you go the NAT route, you don't really need IPv6 as much. Then it becomes a cost issue and a support issue, and it becomes something of a luxury rather than a necessity.
Is there somewhere an upto date analysis of the costs per country/areas of IPv6 vs IPv4? This is the "ultima ratio" of a move and of the selection of an application to promote IPv6. Without an architectural and economical network model could people take decisions. Lobbying will make them interested, money will make them decide.
jfc