As he explains you don't need an ipv4 address for every person. Just give em a shared one and use NAT. Our entire office has just one public IP address and nobody knows the difference.
NAT works in an office environment because most offices aren't doing anything more than web and email. Home usage scenarios are significantly broader and harder to keep working behind carrier grade NAT.
As technology filters down to the third world, and (assuming there isn't some massive device convergence that reduces demand for IPs in the first world) the ratio of devices to people will rapidly become skewed. It's a lot easier to pump out cell-phones than babies after all :D
If there is even a single customer that only has access to ipv6, you have to support them 4 and 6. My office, and your office will of course stay on ipv4. I'm pretty confident least one university will soon be strapped for cash, and sell of the boatload of their ipv4 space, and just give the dorms ipv6 addresses. there will be much whining and complaining, and everyone will support ipv6 the next week.