Renumbering is *NOT* simple and *CAN't* be automated (no remote company will allow you full automatic access to change things in their setup, think firewall rules for instance...)
Another example. My company laptop has a VPN client which has two IPv4 addresses in for the main and fallback VPN login servers. Even if there are systems in place for updating these settings when I reboot my laptop, that won't prevent helpdesk calls. For instance, it is common for people to put laptops to sleep without logging out. It may be a week or two between logins. If the network is renumbered, suddenly the VPN login service fails and remote users have to call a helpdesk to find out the new IP addresses. Processing a helpdesk call costs money and downtime due to lack of network access also costs money. It is difficult to foresee these kinds of costs. Now, if one or two companies does a renumber and runs into unforeseen costs and problems because of firewall configurations, VPN configurations, IP addresses stored in mobile phones, PDAs, inventory databases, smartcards, etc., then that will become publicised. Once other companies learn of these problems then they will refuse to renumber and will begin to demand fixed address assignments, i.e. PI addresses. The only way to convince these companies to renumber will be a protocol upgrade such as IPv4 to IPv6. I believe that the majority of companies will not be willing to accept renumbering after they have migrated to IPv6. The IPv6 migration will be THE LAST RENUMBERING!!! --Michael Dillon