Just below 30m. Sequel will cut into it's legs, but not that much.
Bonus: Breath of the Wild is the most successful games in the series by a mile. Arguably the greatest game ever. Even Nintendo aren't crazy enough to mess with that formula too much. From the trailer I'm guessing there might be more focus on narrative, so maybe the world and progression will be less free and open. But overall I'm still expecting more of the same with improvements.
Freedom is the key factor. Aonuma still doesn't know what Zelda's core is. Zelda focused on narrative is an anti-root Zelda by default. These are not Lolo's adventures, although Aonuma wants it so badly. There is no use waiting for someone who was unable to finish the original game, who likes the original game. BotW only came out that way, it seems, because they placed the puzzles in a controlled way in the shires and in the dungeons, they contained Aonuma's impetus, leaving the universe alone with the player to build his own narrative.