I don't think there's a need for "a clear winner" since gasoline, or a blend compatible with it will be staying with us for a long-long time. Butanol, plankton oil, or some other heavier alcohol could possibly be used as a direct replacement, maybe with a bit of added dino juice distillate. Same with diesel -- it's here to stay, whether it's bio, dino, etc.

One change I can see with gasoline, however, that instead of the usual 3 pumps (normal, mid, super) there will only be a single pump with a pushbutton or dial selector for grade. And diesel will probably become mainstream even in the US, and the majority of new cars will be hybrids since they're superior to others in cities.

The two other options will be hydrogen once the technical hurdles are resolved, and electricity, either using some kind of battery, or a fuel cell.

Of course, this is all IMHO, but I'm 99% sure on all my choices except hydrogen. However, by the virtue of no greenhouse gases, I think hydrogen will win over ethanol, or gaseous fuels containing carbon like CNG/LNG/propane/butane/etc.