Obviously, Smith knows this, since he has published papers on the legality of self-driving cars as late as 2012. The purpose of the quote (for me) is to draw an analogy between Strong AI and self-driving cars, both of which have had people saying "it is just 20 years away" for many decades now (and one of which is now here, making the people that made such a prediction 20 year ago correct).

By principle of charity (everyone knows about google cars by now), I took the grandparent to mean "past performance is not a guarantee of future returns."