I suppose there are two issues here.

Carbon footprint

Diminishing fossil fuels.

Battery only and hybrid cars of today are the prototypes for tomorrow's generation. I have looked at hybrids for my next car, although I doubt I shall. Just not quite there yet. The BMW diesels tick many boxes for me, including being very clean.

If you want low carbon footprint then consider the huge carbon footprint of the batteries. The Prius batteries have had their components shipped around the world including USA, one of the Scandinavian countries and Japan before seeing a car and the factory emissions making the things is incredibly high if an article in New Scientist is accurate.

If the principle is diminishing fossil fuels then diesel engines are the most appropriate for long distance, small petrol for city use.

The infrastructure we have for refining oil into fuels would need to be reciprocated in size and cost in order to commercially produce hydrogen in sufficient quantities but hydrogen engines, already on sale in Los Angeles (where the pumps are!) by Honda have to be the way forward.

One thing of note. Petrol engines made by and for areas of the world where fuel is expensive are far more economical and clean. The USA doesn't do too good in that respect and whilst Ford Europe are getting 180BHP out of a 1 litre engine, Ford USA say the low quality of the petrol in The States, because that's all prices can stand, preclude using such engines.