I don't expect fast transition to IP6 and sending IPv4 to history. IPv4 will be with us for a long. These protocols will exist paralel and IPv6 would take more and more percents of network traffic. When some Enterprise understand that is too complicate to cope with IPv4 and short public address space it would get IPv6. It will be a massive transition at one moment. Something like Gauss function with time on X and number of transions to IPv6 on Y axis.