OK, but that does not solve the problem where the NATs are mostly deployed
-- home and SOHO -- until all internet servers of interest to those users
speak IPv6. "Can be upgraded to do so" is great if you control the server,
but these users don't.
true enough. fortunately, NAT doesn't interfere much with www and email,
and a few other common services, so NATted v4 works okay to access these.
IMHO v6 will mostly be used to talk between things that don't work with
NAT. for those things, it's worth it to upgrade the hosts. and 6to4
relives some of the immediate requirement to upgrade the net.
Keith