Initially those transit providers and ISPs that do offer IPv6 transit will be able to charge for this service as it will be a premium value add.  However I can’t see this business model being able to last for more than 6 years (through to 2012), and possibly only three years.

After this point in time I expect IPv6 deployment will be standard, and will no longer be a premium service offering – it will be the standard offering, like IPv4 is today.  Once IPv4 has become exhausted and you can’t actually give a customer an IPv4 address then you definitely wont be able to charge more for IPv6 – otherwise the customer will walk.

So do providers start implementing slowly now, and recoup some of their investment while they can, or wait till they are forced to do the upgrades and are not able to recoup any of their “new” investment.  Rhetorical question.