IETF working on IPv4.1 as alternative to IPv6
packetlife.net
packetlife.net
I now consider IPv6 to be a textbook example of how not to design a protocol. It would have been hard enough to advance us all to IPv4.1, but transitioning your stuff to IPv6 is terribly harder than it should be. For any serious network program it's like ripping out your spinal cord and putting a new one in. It's no wonder it has basically failed to date, it has proved much more work than I would have expected to actually convert software to use it, let alone use it properly.
It might still be faster for the Internet to actually create IPv4.1 right now, get to consensus, and fully deploy it, than to fully deploy IPv6 from where we are. Probably a close thing.
So carrier NAT and overlapping numbering suddenly looks real good to everyone. Except for the network engineers.
End user equipment (esp things like phones, blu-ray players) is a different story in terms of readiness, but this can be handled at the border.
Supporting IPv6 is absolutely nothing like "ripping out your spinal cord and putting a new one in". It's largely trivial if you aren't doing anything tricky--and, notably, it requires nothing that an IPv4.1 wouldn't require. The Berkeley socket API was designed with support for multiple protocols from the start, so you shouldn't have to touch much beside your address structures and name resolution code.
And I say this from the standpoint of someone who added DHCPv6 support to a DHCPv4 server, which actually is tricky, since DHCPv6 is an entirely different protocol from DHCPv4 and substantially more complicated to boot. It still wasn't all that bad.
Most importantly, IPv6 is done. It's been done for years now. The router support is there. The OS support is there, with the exception of some laggards who really should get around to implementing DHCPv6. It's in active use. (Do you have a DOCSIS 3.0 cable modem? Congratulations, you're using IPv6!) The biggest obstacle to deploying IPv6 is just doing it, and again that's not going to be any easier with an IPv4.1.