If you are an ISP running dual stack ipv4 with NAT plus ipv6, the more connections happen via ipv6 and the more traffic happens via ipv6, the better, because it doesn't have to go through the NAT infrastructure which is more expensive, and cost scales with traffic (each packet needs its header to be modified) and number of parallel open connections (each public v4 address gives you only 65k port numbers, plus this mapping needs to be stored in RAM and databases).