The Nintendo Switch already has two games in The Legend of Zelda series in development, but there may be a third one on the way, as a recent job posting from Monolith Soft suggests that they are working on the next entry in the series.
Monolith Soft is a video game development studio that is currently owned by Nintendo and has produced exclusive titles for Nintendo systems since 2007, and was involved in the process of developing The Legend of Zelda: Breath of the Wild. Nintendo recently announced that The Legend of Zelda series would be crossing over with Crypt of the NecroDancer in a game called Cadence of Hyrule, which means that they are allowing an indie developer to use one of their most iconic first-party franchises. The Switch port of The Elder Scrolls V: Skyrim also included content from The Legend of Zelda series, as has Mario Kart 8 and Mario Kart 8 Deluxe.
It seems that Monolith Soft will be heavily involved with the next Legend of Zelda title, as Nintendo Everything is reporting that the company has posted a job listing on Twitter for an entire development staff that is meant to work on a Legend of Zelda game. The job post is looking for designers, programmers, planners, and more, with a link to the Monolith Soft recruitment page.
Monolith Soft's involvement with the next Legend of Zelda game isn't too surprising when you consider that they worked on the last few titles in the series, but the job posting is suggesting a far bigger role than before, to the point where they may be handling the game themselves. The Nintendo Switch currently has two upcoming games in The Legend of Zelda series - Cadence of Hyrule and the remake of Link's Awakening, which would make Monolith Soft's project the third in a relatively short window of time. That probably means the game the studio is hiring for is quite a ways off, since Nintendo certainly isn't lacking Legend of Zelda content for 2019.
Breath of the Wild was the killer app for the Nintendo Switch at launch and there have been rumors about a follow-up game for a while now. The fact that Monolith Soft worked on the original Breath of the Wild might mean that Nintendo trusts them enough to work on a whole new Zelda game, but even if the company is reprising the more supplementary role it had in that game, it's noteworthy. Given all the other studios working on the Legend of Zelda property right now, Monolith Soft tackling another one seems to strongly suggest a Breath of the Wild sequel is coming.
Source: Nintendo Everything