According to foreign media gamerant, the developers of the former Retro Studios announced the concept of two canceled Nintendo works, namely an unfinished "The Legend of Zelda" game and a game project called "Haunt" featuring Kingboo.

You can see that the style of this Zelda game is dark, and it is said that this game is an action JRPG featuring Sheik. And this project with Kingboo as the protagonist seems to be built for the handheld.
Unfortunately, both games have been cancelled. Hopefully, Retro Studios can bring us the new Metroid sooner rather than later.
The Legend of Zelda (Japanese: ゼルダの伝說, English: The Legend of Zelda,Taiwanese translation") is a well-known game series launched by Nintendo. Originally released in 1986 on Nintendo FC, the first title, Hylar's Fantasy: The Legend of Zelda, it developed into a series.
The Legend of Zelda series is one of the most comprehensively rated game series of all time, and is listed as the company's signature work alongside Nintendo's Mario series and Pokémon series. Among them, "The Legend of Zelda: Ocarina of Time", launched in 1998, pioneered the perspective and operation problems faced by 3D games at that time and cleverly combined game design with 3D perspectives, ranking first in history with 99 points in the global media average score included on the metacritic website.
On March 3, 2017, the latest game in the series, The Legend of Zelda: Breath of the Wild, landed on the Wii U and Nintendo NS. Breaking the production framework of the series since Ocarina of Time, the game focuses on open worlds and returns to the design concept of free exploration of the original series, scoring 98 points in the global media average score included in the metacritic website.