The expectation of this article is that Google will somehow shortly produce a car which will completely replace drivers in all circumstances. Clearly, that's the eventual goal, but that's not needed to produce something useful. Car companies are already churning out various incomplete solutions that help with highway driving or parking.
I expect their initial product to be something that works as a taxi in semi-controlled circumstances, or something that makes driving more convenient, but which requires intervention some of the time. Either of which would be a viable product.
Early cell phones were overpriced bricks, but they were still useful to some people. It took a huge investment from many companies and quite a bit of time to get to the point where people considered dropping their land lines. Replacing the old generation of technology is not usually a sudden process, but involves a lot of gradual improvement.