"With nearly 85% of all available Internet addresses already in use, experts believe that, if current trends continue, Internet addresses will run out by 2011."
Others think that IPv4 is just allocated wrong. Why do some companies have a Class A or 2 when they could never use them.
Meanwhile, the DOD has already gone to IPv6. I guess, the Defense Dept. is trying to find out if "the Internet [will] be able to scale to connect billions of people and devices." The OECD has a report that focuses on possible scenarios and on why we need to move to IPv6 (here).
Although many carriers have announced IPv6 networks, my experience in Tampa is that very few actually provide it.