The fact that there's going to be a The Legend of Zelda: Breath of the Wild 2 was the biggest highlight in the long list of Nintendo E3 2019 announcements today. It didn't contain a release date, so we may see it at E3 2020 before it actually launches.
There's scant information about this new Breath of the Wild game, though we know that it's a full game and not simply DLC, and that it's coming to the Nintendo Switch, making to the second flagship Zelda title on the console. Breath of the Wild 2 follows the original game that launched with the Switch on March 3, 2017.
The Legend of Zelda: Breath of the Wild 2 trailer, which you can watch via YouTube above, is just 82 seconds long and there's no dialogue whatsoever.
It features a torch-carrying Link and Zelda traversing a dark dungeon (no big surprise there) and then a message popped up that read: "The sequel to Legend of Zelda: Breath is in development," according to Nintendo.
Nintendo's statement leaves it open to calling this game something besides Breath of the Wild 2, though hasn't revealed an official name and there's very little story to suggest what it may be called in the end. And it does seem as if this is a direct sequel to Breath of the Wild.