The legacy Class As really aren't a significant issue either. By the time you subtract out all the effort that the clawback itself would involve (nontrivial reconfiguration of quite a few major corporate and government networks), it would probably be a wash or quite close to it versus just trying to work on IPv6 -- which finally seems to be getting some traction.

At best I've heard a few extra months added at current burn rate estimates. Hardly worth the knock-down, drag-out fight that it would involve.