I’ve sat on this idea since the release of Hyrule Historia. And I think it would legitimize the entire crazy timeline, and do what Nintendo must do next to level up Zelda: massively up their story telling. And it combines with this OP idea of the return of the triforce.
This new game does one key thing: it firmly establishes BOTW/TOTK Link as unequivocal successors to the Child Timeline after the hero is victorious in OOT.
BOTW Threequel continues and concludes this Link’s adventure, and is the first Zelda trilogy with Link-Zelda continuity. We’ll call him Blue Link.
After a banger of an opening sequence, Blue Zelda reveals to Blue Link the cause of this “banger sequence” and its solution: there is a relic called the triforce and it must be reunited not only to seal away evil—but to fix space and time, which has been fractured for millennia.
The three dragons—the fairie surrogates—are basically functioning like the TVA (Time Variance Authority) from the Marvel series Loki. Their human forms exist in another realm: the past.
This past is ultimately met.
It is Old Man Link from the Fallen Hero timeline and is the same Link from Zelda II: Adventure of Link. Who is also the same Link from Zelda I. Think Snake from MGS4 Guns of the Patriots, or Logan/Wolverine from the Old Man Logan story.
So this game is the end of a trilogy for Blue Link and Zelda 1 + 2, simultaneously.
And it’s co-op (if desired). As both Links.
The game might as well be called The Legend of Link.