Ultimately, the power for transportation will come from electricity, whether it be directly from electric batteries (tesla motors, chevy volt, etc) or from hydrogen produced by electric hydrolysis. Either way it takes oil out of the equation, which eliminates the threats to our economy and security.
The electricity can then be produced either the way it is now (combo of coal (50%), Natural Gas (25%), Nuclear (19%) and other (Hydro, renewables)), or we can move to where I think we'll ultimately be, which is a combo of nuclear for primary power demands, hydro where it exists now, and rooftop-mounted solar for residential and supplemental.