Fans can rest assured that Mario Kart 8 will indeed feature some kind of DLC. Nintendo has announced that Japan will get a free Mercedes-Benz kart during the summer to cross promote both products. The free download is set to release in other regions as well, but details are not being shared at the moment.
Be sure to check out the commercial for the car itself as well!
httpvh://www.youtube.com/watch?v=_AkgJZGspCM