there is a lot of reasons for tesla to keep the drive train the same or at least similar to the model S/X but from what I have read in my research on electric motors induction motors are not as efficient as the PMAC. Size wise the PMAC can also be smaller, provide more torque, and will run cooler. The only down side is you have to obtain the rare earth magnets from somewhere. And if you over heat them the magnets might be demagnetized. The Chevy Bolt uses a PMAC and it gets EPA 238 miles on the same 60KWh energy that can only propel the model s to 218 miles on the dual motor version or 210 on the single motor version. Countless other EV are also using PMAC or PMSM which is pretty much the same thing. Now some are arguing the highway mpge of the bolt will be less than the model 3 but we don't know that yet. All we know is there is 2 numbers and when you scale one to 55% and another to 45% and add them you get the final mpge and use that to get the expected range of 238 miles. I guess my point is if tesla started using PMAC instead of the induction motor to begin with maybe the original model S couldve gotten 300+ miles EPA range right off the bat. And closer to 400 miles with the new 100Kwh battery.