This increases the motivation, but there are methods of delaying the hard requirement to migrate. A smaller patch is to reclaim unused blocks; a bigger one is c

This increases the motivation, but there are methods of delaying the hard requirement to migrate. A smaller patch is to reclaim unused blocks; a bigger one is carrier-grade NAT. e.g. in some countries such as Russia your ISP will allocate you a 10.0.0.0/8 address rather than a publicly-routable one, and will have a NAT between its customers in your city and the publicly-addressable internet. And yes, this is an ugly solution and comes with a lot of problems and costs.