I think you need to go back to the premise here a bit. The scarcity of taxi medallions was not a feature of their original purpose (to protect riders from unsafe drivers), but a corruption of it (to provide risk-limited profit to the existing holders of them).
I would expect that the profit stream off a medallion is effectively greater than that of any other risk-limited or risk-free investment in a government asset (bonds and such) or they wouldn't be in such great demand even at their vastly inflated prices.
So is, perhaps, the decades of extra profit not compensation enough? Maybe recent buyers have some claim to have had the value of the instrument disrupted, but anyone who's been leaching this system for decades should frankly be happy that the government (and by extension society as a whole) propped them up for so long.
At any rate I expect there would be a gradual expansion of the number of medallions on the market until it was an unrestricted license just like any other, at which point trading or transferring them would become illegal. This would provide some ability for holders to get some of their value back as it lowered.
I would expect that the profit stream off a medallion is effectively greater than that of any other risk-limited or risk-free investment in a government asset (bonds and such) or they wouldn't be in such great demand even at their vastly inflated prices.
So is, perhaps, the decades of extra profit not compensation enough? Maybe recent buyers have some claim to have had the value of the instrument disrupted, but anyone who's been leaching this system for decades should frankly be happy that the government (and by extension society as a whole) propped them up for so long.
At any rate I expect there would be a gradual expansion of the number of medallions on the market until it was an unrestricted license just like any other, at which point trading or transferring them would become illegal. This would provide some ability for holders to get some of their value back as it lowered.