Since most of NASCAR's races are ovals and high bank ovals and the power demands are nearly constant a hybrid is a bad choice for such an application. For road racing, where you're off the throttle and on the brakes a bunch reclaiming energy while braking will reduce energy requirements, but when there's very little braking there's almost nothing to be reclaimed.
NASCAR does a few road races each year but for the few races a hybrid would make sense the costs to develop would not.
An all electric car is even less likely as NASCAR runs LONG races of, like, 500 miles and 500 miles on a battery pack, even if you were driving country roads at 50mph or less is not feasible at this point so racing at 150mph or more is probably an order of magnitude out of the question.
Lastly, since Ford and GM make most of there money selling gasoline cars and trucks there is ZERO chance NASCAR ill do this in your lifetime!
Brian