Circa 2020
Nissan has publicly stated that they will have self driving cars available for purchase by the year 2020 (Nissan Promises to Deliver Autonomous Car by 2020 | Autopia | Wired.com). That is a short enough time frame that they certainly have an actual product in the engineering pipeline as we speak. Several other companies are actively working on the technology, so somebody might beat them to it by a year or two. Or, the engineering schedules may slip and they will be delayed by a year or two.
Autonomous vehicles are coming. They can't get here fast enough for me.
Bring it on! I think the technology exists now, it's simply a matter of driving down costs. Still a bit worried about an iRobot scenario where the car gets hacked and drives us into a wall though...