Crossovers and cameos have been around almost as long as the medium of gaming, but having guest characters is pretty indispensable at this point. Series like Soulcalibur, Final Fantasy, and Yakuza have all recently used crossovers to spice up their franchises, and Mario Kart’s fairly static roster could really use something like that to freshen things up.
Who should join Mario and his friends on the track? If Nintendo wants to keep things uncomplicated, the next game could just add other Nintendo characters to the game, like Link, Pikachu, or Kirby. And if Nintendo is feeling more generous, they could open the floodgates to include characters from friendly third party publishers like Namco, Capcom, or Ubisoft. making the tired collection of Mushroom Kingdom residents feel fresh again.