[smaudet]

The solution should be to use IPv6 everywhere via 4to6 and 6to4 protocols. Then Ipv4 usage will become less important (as fewer people will want to maintain or use it), and ISPs will have an active incentive to switch (less network translation to maintain).

At that point, the main consumers of IPv4 will be old devices and legacy clients that for whatever reason can't support IPv6. Nobody will be paying for ip's otherwise, so ISPs can continue selling their business plans as normal, the rest of us can just use IPv6 and not worry about rent-seeking behavior from the exhausted IPv4 space.

I would guess, around 50-60% penetration, you will start to see real "only works with ipv6" behavior, and the trend will accelerate...its already at 30% which is enough incentive to at least try to get on IPv6 now if possible...