So given Elon's announcement yesterday that the semi will indeed be long haul, I have a theory to put out there. I don't believe the next versions (350kW or above) of the supercharger will be meant for the cars (S,X, 3) but instead for the semis. Given the peak performance levels of the S and X, the maximum amount their motors can handle discharging at once is around 400kw. So that's more or less the limit of the wiring internal to the car to receive a charging current from a supercharger. To install a separate series of wires to allow just for faster charging that the motors can't handle is in my opinion a waste of weight, and expense. If you have the semis though with a BAB (big ass battery) then this supercharger amount makes perfect sense. The only time truckers are making money, is when they're driving. So the supercharger will have to be massive to be able to get the battery back up to "full" so it can get back on the road. This also helps the concept, because now you don't have Model S, X, & 3's taking up room on a supercharger that would prevent truckers from making money. So given Musk so far has never explicitly said that the next version of the superchargers will be for the cars, I'm throwing it out there they'll be for the Semi.