I wouldn't say it never comes. There are ISPs in (at least) Ireland and Germany that have forced customers to share IPv4 addresses recently. You lose control of your ports because of this. So your kid, for example, can't host a Minecraft server because the ISP's router doesn't let you.
Well, Germany, they don't even have cell phone coverage in every village. And where they have it data rates can be abysmal. Yesterday the news hit the mainstream media that Nokia got a NASA deal to build 4G on the moon. Couldn't resist thinking building it in Germany would be more useful.
Disclaimer: I lived in the county over 30 years and still have strong links.
Presumably there will come a point where the cost of purchasing enough ipv4 addresses outweighs the cost of making a project work with ipv6. It'll be an interesting piece of economics to see where that boundary is.