I won't comment on the apocalypse scenarios you described, because the possibility is obviously there. But regarding the MAD scenario on roads, I believe with self-driving cars you're trading off ability to survive in very rare cases (like split-second decision after reading the face of the driver about to crash into you) for having the usual accident causes (speeding, distracted driving) not happen.

My hope in the transition period is that the presence of self-driving cars on roads will finally force the drivers to start obeying traffic laws - which should pretty much eliminate the MAD consideration altogether.