2) Anyone care to guess how much network gear is deployed that either
won't or can't be upgraded? i.e. Old cisco gear without the RAM and/or
flash to handle a newer code train...the old one in use long since
unsupported, or gear from vendors that no longer exist? As long as this
stuff generally works, nobody's likely to replace it.

Scott Weeks wrote:

I have seen a LOT of that equipment out there in places like universities and whatnot.

Eventually this stuff falls out of the internet or gets consigned to
roles where it can't do much in the way of damage. The timescale over
which this happens is extremely long. ipv4 exhasution has it's own
timeline and I daresay most network operators will be focused on:

  Deployment of new resources (ie deployment of ipv6)

  Not causing damage to or requiring modification of the installed

It seems clear to some if not to everyone that use of 240/4 requires the
modification of the installed base.

IPV6 deployment is not going to affect the installed base with the
exception of the devices that already support it. the ipv4 internet will
continue to operate as it does today except perhaps with additional
pressure on address space constraints, growth of large nated space and
erosion of end-to-end reachability.