If you live in a major city and haven't seen an autonomous vehicle yet, you probably will soon, but if you want to buy one for personal use, it might be five or ten years. The NYT has a story on the state of play.
The basic conclusion is that limited applications like buses and maybe taxis in central cities, farm tractors, and long haul trucking are pretty close, but all weather operation on all roads, not so much.
Right now this technology is driving big chunks of both artificial intelligence and sensor technology. The side effects of these developments may be even more important than the transportation revolution they will bring.