I thought that was like the Voyager leaving the solar system story that keeps repeating every few years but never seems to actually happen.
Only meant partly in jest. When they start to get really rare, the price of IPv4 blocks will keep going up, until some institutional holders of large blocks start selling. It could take quite a long time before it's really gone for good.
Because while it might be a lot of effort for the large institutional holders when they've historically allocated stuff assuming they have the whole huge block, eventually the price-cost trade-off will reach a point where the address space is valuable enough.
ARIN is going to run entirely out of IPv4 addresses for general distribution in April of 2015.
It's not going to be long before you'll need IPv6 if you want to do anything peer-to-peer.