The Child timeline is truthfully the only timeline I care about and actually like.
Like, the adult Timeline is pretty much a post apocalyptic Hyrule, and while I love WW, I just can't bring myself to like the DS games or the boring water filled wasteland that Hyrule had become. Not to mention Ganon is dead in that Timeline (WW Link wasn't the Hero Incarnate, so when he killed Ganondorf he effectively destroyed the eternal curse brought upon him, Ganondorf, and Zelda.)
It is plausible that BotW occurs in the fallen timeline though.
Aonuma made it pretty clear that "Link does something that causes Hyrule to become like this" What does he do? He runs away or gets defeated. Either way, he either puts himself in stasis, or the sages quickly put him in stasis in hope for the future, and the "hero" we've seen in the past games in this timeline isn't really the Hero incarnate. The Hero incarnate has been asleep, and at some point Ganon breaks free after Zelda II. This ends up leading to Hyrule's overall destruction, and it's some time after these events that the true Link wakes up.
We'll essentially get to see the events that cause this timeline to come into being, and we also get to see it resolved by a cowardly hero that will become the courageous man he was meant to be.