There seem to be a number of 3 wheel concept vehicles I've seen. BMW (CLEVER Concept) for example has one. These car/motorcycles have to get decent fuel economy. They may not be hybrid in the sense of engine technology. But they could sure be considered hybrid in the sense of a cross between a car and a motorcycle. Certainly they would be more 'hybrid' than the smart for 2 (which is close to being a 4 wheel motorcycle.)
I would certainly be interested in a 3 wheel vehicle (a motorcycle with a passenger shell) that would let me get to and from work more efficiently and in the rain (here in Seattle) without getting wet.