There are two major steps that Uber needs to make before achieving their driverless dream.
1) Achieve driverless tech at a safe enough level that they don't carry a huge insurance/legal cost
2) Build out a fleet of cars, maintenance regiment, security team etc.
1 seems to be a huge sticking point for them. And for 2, uber has never had to have large carrying capital costs. They spend on ads, subsidizing rides and legal battles, not purchasing and maintaining vehicles.
Right now they have successfully externalized a lot of costs to their drivers. That will go away. They also still won't have customer lock-in even if they achieve the dream. Others will be hot on their tail and then they'll be back to a race to the bottom where the core competencies are: fleet maintenance, ride optimization and capital costs that far outstrip their current operation.
They have an advantage in ride optimization, not the rest of it.