For a businessman who perpetually struggles with broken promises, Elon Musk gave himself quite a to-do list Thursday night at Tesla’s long-awaited Hollywood unveiling of its driverless robotaxis. After traversing the fake streets of the Warner Bros movie studio set in a sleek, silver two-door “Cybercab” prototype, Musk promised that the company’s popular Model 3 and Model Y vehicles would be able to operate without driver supervision in California and Texas by next year. Tesla will sell those, too, Musk said, eventually for $20,000 to $30,000 a piece.