The following article provides further details on this important issue:
Here are a few excerpts:
"Many expect some disruptions as the IPv6 shift takes place. Web sites could be slow or inaccessible, companies could have a harder time setting up new services, Internet service providers could have a hard time keeping up with subscriber growth, and security will have to adapt to the new technology.
The Net won't collapse, though."
"Perhaps the best news about the IPv6 transition is that, once it's mostly over, the Internet will be a qualitatively different place. With vast tracts of IP addresses available, individual ones can be assigned to phones, computers, cars, stereo components, living-room thermostats, heads-up display glasses, wristwatches, home solar panels--you name it. Where a case can be made for networking, these devices will be able to communicate directly without the network topology shenanigans such as network address translation necessary today."