NYTimes devotes its magazine this week to the subject of driverless cars. One prediction of 2-5 years for the most ambitious cars which might work for my case. I'm somewhat dubious over some of the crystal ball gazing, but we'll see.
My own predictions: driverless vehicles will take off first in niche markets: long distance trucking, Uber/cabs, the elderly. They won't progress as fast with the mainstream of drivers--people like to control their lives and many will be impatient with the granny-like driving that adherence to rules will foster. A key will be relative cost: some of us will pay a premium for driverless cars, others will wait to benefit by lower costs on a per-ride basis.
As time goes by we'll have to change the traffic rules, but that will be difficult with a mixture of vehicles.
One big hurdle will be rural areas. At some point, population density will be so low that a driverless Uber/cab service doesn't make sense--it will take too long for the vehicle to get to the user. For such areas the cost of the driverless car will have be to be less than the cost of the driven car.