Daimler is cogitating over making a four-passenger Smart Car and selling it in the U.S. The two-seat Smart Car took several years to cross the Atlantic from Europe. Sales have been higher than expected by the Daimler folks. So now they're thinker bigger for the future.
The Smart website says in some areas there is no longer a waiting list.
So the sub-compact field is getting highly competitive. I blogged about the Toyota iQ coming to America. And then there's the VW up! VW has said they MAY bring their little car to the U.S., once considered a market anathema to the little urban-style minicars long popular in Europe and elsewhere.
Right now the major attracton these little cars have for buyers is their fuel efficiency. All use standard gasoline engines but get 50 MPG or more. They also take advantage of minimal chasis and body weight of the car itself. So fuel prices, including gasoline tax rates, will continue to have major effect on sales of the sub-compacts as they are made available to American drivers.