The proof of concept is already here, but the technology still needs too much human supervision to be cost-effective. If you want to make self-driving taxis cheap enough for most people to use daily, the prices have to be something like $2/trip.
To recoup the billions of dollars they've invested in it, it might be a decade before we get down to $2/ride. As far as how much human supervision it takes, we don't actually know the costs of it, though the latency involved means it's not Actually, Indians remote piloting the vehicles with Playstation controllers.
