Agree with Johan. ISTR seeing pix of battery winding machines, and got the impression that it's very easy to change form factor: just load a different set of foils, adjust the feeders - and go! (Somewhat simplified, for my own understandingI thought the Gigafactory was producing cells that are physically larger (10% in height, 10% in diameter) than the 18650s used in the Model S / X. How would ramping the Gigafactory up earlier expand capacity for the Model S / X? Would they redesign the battery pack for the larger cell? Would there then be some Model S / X vehicles with the 18650 and some with the larger format battery?
Of course, this supposing we are still winding cylinders, only changing dimensions. Pouches would need a different method.