The Mario Kart series is one of the biggest Nintendo franchises in terms of game sales, as the past few Nintendo systems have had Mario Kart games as their best-selling titles. The Nintendo Switch already has one incredibly successful Mario Kart game, but it's a port of an older title and there are still several years left in the console's lifespan, so there is a chance that another game in the series could be released on Nintendo Switch.
Nintendo has only ever released one Mario Kart game per handheld and home console, but the success of Mario Kart 8 Deluxe means that Nintendo could go in a new direction for the next entry in the series, one that could bring in more characters from different games.
Mario Kart 8 Deluxe Is Selling So Well That It Doesn't Need A Sequel (Yet)
The Nintendo Switch had a jacked roster of titles for its first year, as Nintendo wanted to avoid the mistakes of the Nintendo Wii U and the long gaps in its library. It's for this reason that Mario Kart 8 was repurposed as Mario Kart 8 Deluxe, in order to ensure that the Nintendo Switch had a Mario Kart game available for its first year.
Mario Kart 8 Deluxe has been incredibly successful, as it has been the best-selling Nintendo Switch game throughout almost the entire run of the system, with a current sales number of 19.01 million units. Mario Kart 8 Deluxe keeps reentering the sales chart whenever a prominent holiday happens or when a new Switch revision is released, which means that the game isn't likely to be kicked from the top spot.
The fact that Mario Kart 8 Deluxe keeps selling two years after its release means that Nintendo has no incentive to release a new entry in the series during the lifespan of the Nintendo Switch. Mario Kart 8 Deluxe was released so early in the Nintendo Switch's lifespan that there will be a long time before a new mainline entry in the series is released if one doesn't count the abysmal Mario Kart Tour.
It's possible that a new Mario Kart game could be released for the Nintendo Switch, but it could go in a different direction in order to not compete with the sales juggernaut that is Mario Kart 8 Deluxe.
Mario Kart 8 Opened The Floodgates For Nintendo Characters To Appear In The Series
The Mario Kart series only used Super Mario Bros. and Donkey Kong characters for its rosters until Mario Kart 8 added DLC to the series for the first time.
The DLC for Mario Kart 8 included Link and Hyrule Castle from The Legend of Zelda series, the Blue Falcon and multiple stages from F-Zero, an arena based on Excitebike, and both Isabelle and Villager from Animal Crossing, who came with a stage that had different seasonal variations. Mario Kart 8 Deluxe also added the Inklings from Splatoon, who had their own Battle Arena.
Mario Kart 8 Deluxe is already looking like a Nintendo crossover game, so it wouldn't be too much of a leap to take the concept further.
The Next Mario Game Could Be A Spin-Off That Crosses Over With Different Nintendo Franchises
If Nintendo wanted to make another Mario Kart game during the Nintendo Switch generation without diluting interest in Mario Kart 8 Deluxe, then it could create a spin-off title that adds other Nintendo franchises to the mix. There would still be a few Mario characters and stages present in the game, but the roster and items could be totally overhauled in order to include a wide variety of first-party Nintendo characters.
Nintendo has such a wide variety of well-known franchises that it could easily pull together a compelling roster of characters and stages for the game. There could also be a few third-party representatives from companies who frequently work with Nintendo.
It Could Use The Diddy Kong Racing Approach To Differentiate Itself Further
A straight-up racing game that replaces Mario characters with different Nintendo heroes and villains might not be enough to draw in the audience that already owns Mario Kart 8 Deluxe, so a change would be needed to differentiate the gameplay styles of both titles.
A theoretical Mario Kart successor could follow the example of Diddy Kong Racing and introduce new vehicle types, such as airplanes and underwater vessels in order to add verticality to the stages. The game could also add a story mode with quests in order to add a significant single-player component to the game.
The real way a Nintendo-themed Mario Kart game could differentiate itself is by focusing more on the battle aspect of the game, which is a concept that has sometimes been shaky in its execution in the other Mario Kart games.
Which Characters & Stages Would Make It In?
The Super Mario Bros. universe would still be heavily represented in a Nintendo-themed kart racer, with Mario, Luigi, Princess Peach, Bowser, Donkey Kong, and Yoshi likely to make the cut. The Rainbow Road would almost certainly return as a stage.
Link and Hyrule Castle have already appeared in Mario Kart 8 Deluxe, but a version of Princess Zelda from The Legend of Zelda: Breath of the Wild with a Guardian-themed kart could also appear, with a stage based on the version of Hyrule from the same game.
Mario Kart 8 Deluxe featured some F-Zero content, but Captain Falcon could finally make his return as a driver in a Nintendo-themed kart racer. Big Blue and Mute City could also return in different forms that more closely resemble their original appearance. The Animal Crossing characters could return and be joined by Tom Nook, with a stage based on the island from Animal Crossing: New Horizons. The Inklings would be an obvious choice and Moray Towers would make for an excellent stage with its dueling towers.
The two most obvious franchises to be represented in the game that wasn't already in Mario Kart 8 Deluxe are Metroid and Star Fox. Samus and a kate based on her gunship would be a natural fit, with a stage based on the planet Zebes, as would Fox McCloud in an Arwing kart, with a stage based on Corneria.
The Pokémon franchise would need to be represented with Pikachu riding in a kart. There a ton of options for Pokémon stages, but a Victory Road that acts as an underground cave stage and something set in the Wild Area of the Galar region makes sense.
Kirby has already appeared in a racing game in Kirby's Air Ride and it would make sense for him to appear with a star-themed kart, alongside King Dedede on his bike (assuming motorbikes return as well). Dream Land would likely be the Kirby stage.
Olimar and his Pikmin buddies could appear in an S.S. Dolphin kart with a stage based on the original Pikmin. Ness could appear in a Runaway Five's van kart with a stage based on Onett. Pit could appear in Lightning Chariot kart in a stage based on Skyloft. There are a ton of options available to Nintendo when it comes to first-party characters and the third-party devs would also likely line-up for a piece of the DLC money.