Sean;
Then ask yourself, as an ISP, what benefit you get from IPv6.
My answers: not a chance, none, and zero, respectively.
Don't you think it a benefit that you are allocated a large block of IPv4 address space if you support IPv6? <draft-ohta-address-allocation-00.txt> says: Usage Based Address Allocation Considered Harmful The current usage based IPv4 address assignment policies might have prolonged the useful lifetime of IPv4 address space but this has to the detriment of the the end-to-end architecture of the Internet. This memo proposes the adoption of an address assignment strategy that releases large blocks of IPv4 address space into the Internet. The objective of this policy is to encourage healthy Internet deployment models with end-to-end transparency and association of permanent connectivity with a stable IP address. This is intended to encourage provider support for open transparent Internet service environments that can be sustained with the adoption of IPv6. and there will be some experimental assignment "soon".
| At some point, when ARIN just stops issueing IPv4 address space, | I would say it would be in a {I,N}SPs best intrest to switch.
This is not "soon".
That's why usage based address allocation is considered harmful. However, deployment of the policy in the draft above makes it real soon. Of course, more serious problem is in multihoming but the solution, as usual, is to rely on the end to end principle as described in: draft-ohta-e2e-multihoming-00.txt Masataka Ohta