moving to IPv6

I agree 100% when it comes to payload, but network addresses serve
the network as much as the packet. To the extent that we start
deploying networks with more functionality (such as mail relaying
and web caching), then the same logic applies to DNS names.

One big problem we have today is that transport addresses have
embedded within them network addresses. To cryptographically protect
transport-level connections in practice means that network level
addresses (i.e., those in the IP header) cannot be safely modified.

Sure, we can say "that is broken and must be changed", but doing so
will not be painless or free and begs the question as to whether the
total cost of doing this exceeds the benefits NAT brings. It is
questions like this that make me question whether we fully understand
how scalable/viable NAT really is for the long term.