it's not as easy as that, and not very new idea. Some RIRs (Regional Internet Registries) do not allow that. you would need to find some legacy space to do it, which it may be hard. and then some buyers. also you only have a few years to recover your investment, by the time ipv4 is finished (not the IANA pool, but the actually stock from rirs), probably ipv6 would be a reality.