Thousands of drones? What pray tell will they be doing? What makes you think they'll all be needing an ATC service? I already see a screen full of code 1200 blow flies buzzing around and rarely provide a direct service to any of them. Unless I can be guaranteed real time two way comms and following of controller instructions, i.e. behaving like a manned aircraft, they won't be getting a clearance in my airspace.