It's kind of funny that doing so would have been easy years ago; but the easier it is to just transition to IPv6, the harder it is to drive up the price of IPv4, as decreasing supply of IPv4 at this point will just drive down demand. Yes, you're "making IPv6 take off" in some sense by doing so, but not in a positive-feedback loop; more in a negative feedback-loop, where the market ends up in a new equilibrium state where nobody is switching.

Which is exactly why IPv6 never should have required transitioning off of anything.

There were IPng proposals in which zero-padding an IPv4 address gave you a valid, interroutable IPng address. One network is a strict superset of the other.

Greenfield redesign was a great idea, until the ipv4 fire NATion attacked ...