I know this comment is a couple of days old, but neither Uber nor self-driving cars in general will come close to completely disrupting mass transit. It might disrupt suburbia, where you get a bus every 30 minutes with 10 people on it - and transit agencies will probably be delighted to no longer have to offer this non-profitable service. It will do nothing to high-capacity transit that moves tens or hundreds of thousands of people a day - not only because of economies of scale but also because there's no road space for that many cars, self-driving or not.