Untrue. All one needs to pump gas is a generator, and generators can be powered with propane and natural gas, as well as gasoline. In the event of a hurricane or winter storm that knocks out power, power gets restored in a somewhat reasonable time-frame. It's typically not worth switching over to an alternative power source for the pumps.
But if our nation was attacked, by terrorists for instance, one of the prime targets is our power grid. And in that case, a region of the country (lots of people) might be without power for quite a bit longer than is typical with storm-based outages.
In that event, gas stations would start using other sources to pump their gas.
I would think that, eventually, we'll see natural gas or propane backup generators at public charging facilities. At least I hope that, for emergency management reasons, that, or something similar happens before too many of us are relying fully on electricity for transportation.