I'm too lazy to work on motors so I would prefer brushless take over, but the guys who have done their homework and are willing to go through the time and expense should have somewhere to race.
Unless brushed and brushless stock are forced to compete head to head, I think there will aways be a brushed stock motor class. For every guy who hates to ever touch his motor, there's another guy who won't race unless he can work up his motor.
I'm already seeing guys who are relatively new to the hobby, people who you would assume gravitate towards brushless, say leave stock alone and keep the brushless motors out.