If technology gets good enough batteries become attractive for a wide variety of engines that currently require either electric cords or fossil fuels. Think drones, bicycles, lawn appliances, vacuum cleaners, home UPS, solar energy storage, automated greenhouses, etc. It also could have knock-on effects on the type of powered appliances possible, eg. perhaps you'd want your toaster & cabinet to be mobile so you could have breakfast in bed, but this is impractical with electric cords. I wouldn't worry too much about demand for batteries.