In a brace of tweets, Mario Kart Tour was announced for iOS and Android for a September 25 release.
Pre-registration is available now, with details here, according to one of the tweets:
“Pre-registration for Mario Kart Tour is now available! For more details, please click here: https://promotion.mariokarttour.com/pre-registration/ #MarioKartTour will be available on 9/25. We hope you're looking forward to getting behind the wheel of this new game!”
Nintendo of America had this to say in concert: