By the time they get around to de-regulating the medallion system, self-driving cars will be available, which will put taxi drivers out of business. (Unless they block that too.)
Self-driving taxis will put themselves out of business once they either a) crash, killing/injuring someone, b) are regularly used for illegal activities, or c) deliver someone into a dangerous situation.
If that doesn't happen, the existing taxi industry will surely get into the game to make one of those happen, tout-de-suite.
