Buying Xbox and changing their mind to a modern, targeting a worldwide user: the traditional core gamer. Not their lifetime fans that are the ones buying WiiU and 3DS.
New system would be high end tech to compete with PS5 and modern PCs, and would update Nintendo in all the features and services they have been missing or getting late in Wii and WiiU: proper multiplayer with non-game dependant voice chat, trophies, proper digital games pricing, region free, big ass HDD, cross-buy, cross-save, cross-play, VR, streaming games, better (even more) approach to 3rd parties and indies, etc.
If they are smart, they would release it as a powerful handheld that can also be connected to a tv and use it as console merging both of their markets since in handhelds they are still alive doing a good work.
But this never will happen. They will continue releasing Mario 125, Mario Cricket, Mario Mountain Bike, Zelda 42, Donkey Kong 24, Smash Brosh 9 in an outdated enough machine that makes impossible for 3rd parties to release multiplatform games there, etc.
Most traditional players, who want sports games, shooters and open world games with modern features and the best posible visuals will continue ignoring them, kids will continue playing Minecraft/Skylanders/Disney Infinity/etc and casuals will continue in mobile. They will continue being alonw with their fans, and they won't care because they have a lot of money.