How will we migrate from IPv4 to IPv6?
Network Address Translation (NAT) boxes may be one way to support IPv6 alongside IPv4 in the beginning. But since they involve the translation of IPv6 addresses into IPv4 addresses and vice versa, they do not provide a long-term answer. Furthermore, they prevent the deployment of end-to end IPv4 security. IPv4 and IPv6 are expected to coexist for a number of years, but IPv6 is expected to eventually replace IPv4.