Maybe when Nintendo is about to release thier next console, they will announce a new Zelda game?
Maybe I'm just super cynical, but with the current pattern, they'll wait till the console after that one. Think about it... Wii had one, but it was a Gamecube port, then they came out with one specifically for the Wii but only at the end of its life cycle. Then they announced one they were making for WiiU but only at the end of its life cycle and it turned out to have been delayed for the Switch, same as Twilight Princess for GameCube.
This seems to be the pattern.
* Console in need of its own Zelda.
* Ignore that console till everyone's given up on that console.
* Announce Zelda game
* Delay release of Zelda game till next console
* Use new Zelda game to sell next console
* Only release new Zelda game on originally announced console to avoid backlash
* Never release another new Zelda game on next console until the end of it's life
* Port older Zelda games to console after next console
* Repeat process
So I'm not holding my breath. There probably won't be a new Zelda game until the Switch is dying because the novelty of it has worn off. Even then if there is another for Switch, it'll either be delayed for the console after the Switch, or it'll be the last gasp of the Switch, and the console after it will launch without a Zelda just to get an HD update of Skyward Sword mid way through its life span and maaaaaybe BOTW toward the end of its life span because the fans won't stop complaining. Then at the end of THAT console's life, there'll be another one announced, and what'll it be? Delayed to be a release title for the console after that one.
Don't get me wrong, Nintendo has awesome consoles, but they seem to have lost the plot on both 1st party and 3rd party support