While they haven't said anything about it themselves, Monster Games, a dev team who works very closely with Nintendo, is officially working on a new game, and one that will include Career and Championship modes. This was discovered through a job listing for the company, where they also list the fact that the game has been in development since February 2015. Monster Games has in the past worked on the Excite Truck and Excitebots games for Wii, and more recently has worked on remakes of Donkey Kong Country Returns and Xenoblade Chronicles for 3DS, as well as helping Retro Studios with Tropical Freeze.
I'm not surprised, game devs are always working on something, but it is interesting that we now know two of the modes in the game. It leads me to believe it's a racing game, probably a new "Excite" game (possibly just classic Excitebike?) which to me personally isn't very exciting but I know some people will be happy about it. Still it's 100% possible it's something else since those are kind of vague titles for modes.
I'm not surprised, game devs are always working on something, but it is interesting that we now know two of the modes in the game. It leads me to believe it's a racing game, probably a new "Excite" game (possibly just classic Excitebike?) which to me personally isn't very exciting but I know some people will be happy about it. Still it's 100% possible it's something else since those are kind of vague titles for modes.