I doubt they will before full automated kiosks become a thing. Even then I could actually see them keeping a human order taker / maintenance person there and having the food made by robots.
But the main issue is that customers would take too long without someone prompting them. When I worked drive thru I said a lot of "hurry along" things. Like when people named a sandwich I'd interject "Combo?" and "Coke with that?" as well as "Is that everything". Even please drive ahead.