As long as you're not racing, and not abusing the car at the track, I doubt most dealerships would have a problem with warrantying a tracked car.
However, if you're modding the car for the track, and/or bringing it in for service with bald tires, trashed brakes, a smoked clutch, etc... they'll probably chalk up broken stuff to "abuse" and not warranty it. Which, despite wishing, is actually pretty valid. It is possible to treat the car kindly at the track and still have a crap load of fun... Mazda shouldn't have to pay out of pocket for the people that are truly damaging their vehicles with poor racecraft.