In the same way that sessile (non-mobile) lifeforms proliferate all over the globe, and in many cases probably predate the complexity of animal life, I actually think sessile (non-mobile) robots will be more prevalent and more useful, and arrive much sooner, than what people traditionally think of when they think "robots."
The robots used in assembly lines to build cars are sessile. Traffic lights are currently merely automatons, but could very easily become robots -- in fact a network of traffic lights operating in a pseudo-economy, in concert with traffic sensors, would probably be remarkably much more efficient than current centralized and scheduled systems. Gas stations are trending towards becoming sessile robots, and in fact, at night, when nobody's working there, a gas station equipped with cardreaders and automatic pumps is a sessile robot.
One reason I think sessile robots will be more useful than mobile robots -- and one reason why I think they already essentially exist, and are already essentially part of our society -- is because their cost of integration with existing social systems is pretty near zero. Installing cardreaders, switches, and extremely simple brains on existing gas stations is much simpler than building brand new Refuellotrons or whatever. Same with converting an existing traffic light system to harness autonomous agents for greater efficiency, or setting up a car-building robot in an existing factory.
Here's another example:
On-road warning signs
Could real-time traffic information be projected directly onto the road ahead?
Philips thinks so and proposes attaching laser projectors, each with a rapidly-moving mirror that deflects its beam, to ordinary lampposts. These would be used to project images and words onto the road just ahead of approaching cars.
The solution would be cheaper than installing a large video display and safer too, since drivers would not need to take their eyes off the road. Also, a warning about ice or danger on the road ahead would not need a full colour screen, so the projector could use just a single-colour laser.
Each lamppost would have its own IP address and would connect wirelessly, or via a cable, to a central traffic control centre. The projectors could also tap into the power already used to illuminate streetlamps.
As well as providing warning signs, the laser projectors could paint temporary lanes onto the road, steering traffic round an obstruction, or away from the main highway and onto a side road. It's a neat idea, but how well would it work in busy traffic?
(From the New Scientist's roundup of recent patent applications)
Of course the projects to build a self-driving vehicle are much more glamorous -- but if you think about how AI came to be regarded as the huge disappointment of computer science in the 80s by making overly ambitious claims, a simple robot performing a simple task that makes a minor but very useful improvement for tons of people in traffic every day, that's a much more practical thing to do than a robot car -- simpler, much easier to achieve, and useful for everybody, rather than an arbitrary fortunate group.
In a way it's kind of like the difference between agile development and waterfall dev; instead of trying to build an entirely new world, the real successes in robotics will probably come from people who devise simple improvements to existing systems.
Consider how difficult it would be to sell people on transforming the entire international network of roadway and traffic systems to equip those roads with dynamically reconfigurable lanes; that sounds expensive, complicated, and a nightmare of bearaucratic complexity. Then imagine how easy it would be to sell occasional dynamic lane-drawing in emergency situations to drivers who were already used to these laser road-writers. And then how easy it would be to move from occasional dynamic lane-drawing to frequent dynamic lane-drawing in high-traffic areas; and then imagine telling a city council it's cheaper to make lane-drawing even more frequent than it is to pay for new paint on the highway.
One thing software development is really, really good for is it teaches you how to recognize the kind of science fiction that can actually happen.