Piston engines were already replaced by something more efficient: jet engine. I dont buy that batteries are 'light enough'. More likely we will see modern jet-turboprops even in tiny aircrafts. Or perhaps some sort of catapult for faster take-off.
Which is more important in a given application depends of course, but small turbines are terribly inefficient compared to pistons (or even to large turbines), so I wouldn't expect to see your prediction come to pass.