The Legend of Zelda: Breath of the Wild was one of the most over hyped projects from Nintendo and for good reason; titles in The Legend of Zelda series are usually of great quality and have millions of fans around the world, but what made Breath of the Wild unique was that it was marketed as an open world game like no other in the series.
Upon its release, The Legend of Zelda: Breath of the Wild was met with nothing but praise, getting perfect scores from critics and players alike. With the massive success of the latest entry in the series, it was only a matter of time until Nintendo started working on a new project, and it seems that that time is now.
According to a recent job listing on Nintendo Japan's website, the Japanese company is currently hiring a 3DCG designer with experience in terrain and topography production for things like field and dungeons, and a level designer to plan game events, work on the game's field, dungeons, and enemies.
The listing does specifically mention that the designers need to have an interest in The Legend of Zelda, and the experiencew in field and dungeon design may suggest that this is either a completely new expansion for The Legend of Zelda: Breath of the Wild—one that maybe adds a completely new area—or a completely new title in the series.
Nintendo usually begins working on The Legend of Zelda games as soon as they're done working on the last project, so they are always continuously working on The Legend of Zelda. This also doesn't mean that this new Zelda title is for the Nintendo Switch, especially given that they are still supporting the Nintendo 3DS family of systems, which could also mean that they're maybe working on a new game for Nintendo's other portable system.
Whatever the case, this is certainly great news for fans of The Legend of Zelda since, regardless of the console this game comes out for, they win either way.