This will lead to ipv6-only services pretty soon. As the cost of ipv4 space gets higher and higher you'll see things like VPSes and cloud hosting stop offering a free IP with their services, and eventually businesses will stop using it too.
I can see CDNs colocated inside ISP's internal networks shifting to be IPv6-exclusive at first because there will be guarantees of IPv6 connectivity to the ISP's customers.
...if not residential ISPs then certainly mobile-phone/wireless providers.
The more likely scenario to me is everyone slowly running more and more ipv4 traffic over ipv6.
Home providers will start tunnelling ipv4 traffic over v6 (this is already the case here, termed "Dual-Stack Lite"), computers will start start doing 4->6 translation locally according to instructions given over Route Advertisements, hosters will start providing ipv4 load balancers to make their VMs v4-reachable, etc.
It looks to me like we are heading to world where ipv4 will work forever, but be turned into ipv6 at the first possible opportunity.
I don't see that happening until at least 50 to 70 percent of users use IPv6-compatible connections.
One way to accelerate their adoption, though, could be throttling IPv4 transfers: have, say, youtube or Netflix faster at an ISP that enabled it. Or less lag for online games.
