With nothing to confirm this other than the statement by another poster, I can only state that Kirby is a slow adopter of new fangled technology, until they can prove that it has durability.
They didn't adopt a disposable bag system, until they had a bag system that could function reliably with the air flow without radically compromising the performance.
Kirby did not introduce a power drive (tech drive) until they had technology that they were sure would survive the test of time.
If they are adopting a brushless motor, it will only be after extensive testing to insure the motor meets their standards of Quality, Reliability, and Performance. By adding a brushless motor they will be adding electronics that they have never used before, thus they have testing to prove durability.
It would be a big move for Kirby, I will believe it when I see it, but as I stated before. The worry of carbon dust would be moot, if this were the case.