CGNs are expensive. Why would people prefer to maintain them if the
IPv6 infrastructure was working? I don't get the impression that
anybody wants CGNs around forever.
I don't think anyone wants Windows XP around forever either, but even
though you can argue that newer versions are better, it works well
enough for many purposes, and the switching costs are significant.
Anyone who claims that IPv6 works as well as v4 needs to get out more.
Over in applications land, we still have only the dimmest idea of how
we'll do abuse management on IPv6 mail. (If you're about to respond
with something that starts "you just ...", see the first sentence in
this paragraph.)
R's,
John