This is my limited understanding:
Telsa model 3, from what I can tell, is a IPM motor. The magnets it's using are a series of smaller magnets glued together to create a halbach array.
The way these motors can be thought of is a combination of permanent magnet 'PMAC' or 'BLDC' at slower speeds and a reluctance motor at higher speeds. At slow speeds the strength of the permanent magnets create a lot of low-end torque and works the same way that our DD hub motors do. As the motor speeds up the permanent magnets help setup lines of magnetic force through the metal core in which they are embedded. Magnetic fields have a property called 'reluctance' which is the magnetic equivalent to inductance... meaning that once the magnetic field is setup it doesn't want to change. This effectively turns the entire rotor into a temporary 'permanent magnet'. Reluctance motors, like traditional AC motors, use this property to turn the rotor.
Reluctance motors are able to produce a lot of high speed power, but tend to be unstable and difficult to control at lower speeds. Permanent magnet motors provide a lot of very nice low-speed torque and control, but have a limited RPM range. So this design combines the positive behavior of both.
So I don't think that the Telsa model 3 is about creating a super efficient motor at all. It's more about providing very good low speed torque for it's size/weight while still having very good high speed performance. High torque is a bit counter productive to high efficiency.
DD hub motors are SPM, surface mount permanent magnet motors. So they can't take advantage of the reluctance in the same way that a IPM motor can. They might benefit from a halbach array.. I donno. Maybe to reduce the need for a thick iron backing hoop for the magnets. But it would make the motor more expensive.
But mid-drives and geared hub motors could copy the design. Nicer mid-drives like the QS 3000w motors are nice IPM motors already. If somebody creates a geared motor that uses this design and somehow magically solves the cooling limitations of geared hub motors then it would probably obsolete every other type of motor used with bicycles.
