Consider how long it has taken something as simple as battery-powered vehicles to carve a niche for themselves. After a couple of decades, hybrid and electric vehicles still account for no more than 2% of new-car sales in most countries. Battery prices and storage capacities are finally approaching a point where sales could feasibly take off. But even under the most optimistic of assumptions (say, electrics accounting for half of all new-car sales), it would be 2035 at the earliest before they represented half the vehicles on American roads. Expect fully autonomous vehicles to face an equally long and winding road.
What's the meaning of 'sales could take off' in that sentence? and does 'sales' in that sentence mean general cars' sales?