General availability could be centuries away, if ever. Driving a car on existing infrastructure is far too complex an activity for existing technology.
Driving a car under current circumstances I think involves a lot of what humans are naturally good at but computers are not. People assume if they can do it pretty easy, a computer should be able to as well. But that's not the case. Take speech and facial recognition as examples. It has taken those technologies a long time to develop, and they are still prone to error. But humans do it without even thinking about it. Driving a car is much more difficult, and comes with the risk of killing people if it's done wrong. I just don't see it happening any time soon.
Centuries? We've come a LONG way in very FEW years. You DO know that there are cars out there that beat the DARPA Grand Challenge. The challenge was to conquer a course, completely autonomously with nothing but coordinates for start and end points. Oh, and in 2004 that challenge was to drive between Barstow CA and Primm NV (150 miles). No car made it beyond 7.3 miles. The next year, 22 of 23 entrants surpassed that goal and 5 completed the ENTIRE course. In 2007 they changed to an urban challenge on a 60-mile course and had several finishers.
There's more technology out there than you think.