I'm guessing the New Roadster prototypes wern't possible until the Gigafactory's new 2170 cells were in production (for reasons of energy density and perhaps heat tolerance). So how are they pulling off 200kWh? Here are a few ideas: (1) Switching to air cooling? By pulling out the liquid cooling hardware they could increase cell density by perhaps 40%, thus doubling the number of cells that would fit in the same space. (2) Living with a lot of weight? In a way, weight is Tesla's secret weapon. It makes their cars safer, and increases tire traction for faster acceleration times. The traditional drawbacks are easily overcome with a low center of gravity, even distribution, and powerful electric motors. (3) Using an odd pack shape that combines Tesla's traditional floor-mounted pack with an additional box somewhere else (perhaps under the rear seat)?