The actual bar for deploying self driving cars is that they are safer than some (large?) portion of humans that we already allow to drive. We don't have to do it the safest way or the most efficient way.

I agree that ubiquity is unlikely, but because of cost.

(A high end Mercedes can already keep itself in a lane, slow down the cruise for a slower vehicle and will override the driver trying to crash into things. These systems are environmental, they don't depend on detailed maps. http://www.mbusa.com/mercedes/benz/safety

And they are one of several, not way out in front.)