Nothing happens immediately --- the regional authorities still have some free space left, although some are planning to get more stingy. (The discussion here --- http://en.wikipedia.org/wiki/IPv4_address_exhaustion --- is at least a starting point for the curious. FWIW, the first that's likely to really run out is APNIC, for the Asia/Pacific region, within the next three to six months; the RIRs for Europe and North America expect to run out in maybe a year or so, and those for Africa and Latin America expect a couple of years' left of run room.)
Once congestion hits (a few months to a year), I think ISPs natting ipv4 clients, or demanding a premium price from anyone who wants a routable address, is likely to happen somewhat more quickly than ipv6 to the home. But that's based on no inside information...
Also keep in mind there's likely to be a bit of IP reallocation happening. There are a number of companies with full /8 blocks they can't possibly fully utilize.
The Department of Defence Network Information Centre has 151 million addresses. I'm not sure what they're doing with them but they could probably squeeze by with just 100 million if they had to.
I think mobile carriers will be some of the first to transition. The number of devices they need to connect is exploding, and since they have more control over the devices than general ISPs, they can smooth the transition.
Nokia's been pushing IPv6 for a while. It apparently has a significant improvement in battery life because they no longer require devices to check in and renew DHCP leases as often.
It will take a long time if it will ever happen. ISP's can still assign the old IP's they already have while they roll out new modems with IPV6 addresses.
not quite; there are issues with whether those clients can talk to the rest of the net not yet on ipv6 [like, 90% of it or something]).
What appears to be happening is that people are just now seriously beginning to ask the questions about ipv6. We're seeing stuff like incredible performance penalties, poor routing and a complete lack of 6to4 (and back) support anywhere.
There's a long long slog to go and we're just getting started.
Any ideas of what will happen next? How far are we until some home users with outdated ISPs be blocked from the internet?