Sure, but a self-driving car by itself is of fairly limited utility in a taxi operation; the advantage that they provide comes with the data gathering and analysis system that provides centralized control of the fleet. Automation, as it matures, should drive down the per-car cost and drive up the competitive advantage of the player that can expend the most on central resources.
When you reduce the relative importance of the per-unit cost and drive up the relative importance of centralized costs, you make a market that has stronger natural tendency to form a monopoly, because there is more of a positive feedback loop reinforcing the position of the leading player.
