A new Legend of Zelda game seems to be on its way to development. According to Nintendo's Japanese website, Nintendo is looking to hire a "3DCG designer of The Legend of Zelda Series."
When translating the job page, one can see the various aspects related to making a Legend of Zelda game. Level design, dungeons, and concept art are all mentioned. Clearly, Nintendo is working on something Legend of Zelda related. This does not serve as official confirmation of the next big 3D game. Rather, this is Nintendo looking to hire someone to work on a Zelda game project. What that project is remains to be seen. It does sound like Breath of the Wild's followup could be on the way.
The Legend of Zelda: Breath of the Wild released in 2017 to critical acclaim, receiving game of the year awards from numerous outlets. Nintendo continued to support the game via DLC, releasing The Master Trials, and later The Champions' Ballad. At this point, it doesn't seem likely that Nintendo will add any more content to the game. (Next month, it will be a year since The Champions' Ballad.) Thus, it would make sense that Nintendo is beginning to work on its next 3D project. What can we expect from the next game in the series?
Back in 2017, Breath of the Wild producer Eiji Aonuma talked with Famitsu about the future of the series. As translated by IGN Japan, Aonuma was asked if future games would retain the "open-air concept" introduced in Breath of the Wild.
Eiji Aonuma: "From now on," "this will probably be the standard form. However, eventually that in itself could become seen as 'Zelda as usual', and we would start to hear opinions this way and that way. This has always been the case, and the result of what we have made is ‘Zelda'."
Based on this prior statement, it seems like we can expect to see more open-world design in future Zelda titles. Of course, things can change, so this statement doesn't serve as official confirmation that the next Zelda will have the open world of Breath of the Wild. But, Nintendo knows that most fans enjoyed the open world of the game. There's no denying it; Breath of the Wild has one of the most expansive open worlds in the history of gaming. Of course, every main Zelda game is different, with different dungeons and areas. So, if the next game features an open-world, one can expect a different land to explore.
Breath of the Wild took four years to complete, according to Nintendo. One can infer from the job listing that Nintendo is in the very early stages of developing a new game, so it's not too likely we'll be hearing an official announcement anytime soon.