The idea of solving the problem by reclaiming IPv4 addresses was considered, but the math doesn't work:
Now, average daily assignment rates have been running at above 10
/8s per year, for 2010, and approached 15 /8s towards the end. This means any reclamation effort has to recover at least 15 /8s per year just to break even on 2010’s growth. That’s 5.9% of the total IPv4 address space, or 6.8% of the assignable address space.
Looking at the
In addition, reclaiming IPv4 addresses is far more expensive than rolling out IPv6, and it's hard enough to persuade companies that they need to roll out IPv6.
And the calculation for class B allocations is even worse, because you have to deal with a lot more organizations; the cost is higher for far lower returns.