Well yes there is/ or will be less motor maitanance on the brushless motors. But think about the rest of your car. Mod is a very competitive class, and at the speeds they're running, only other parts of the car will wear faster. Drivetrain, ect. Plus the way manufatures are making their cars, they want them the lightest as they can get. Which means they might need to make parts a little more brittle.
Mod will be very popular soon, due to LiPo and brushless. But if its going to be cheaper, and less maitanance?