I have a small theory of the story to be revealed
Hyrule Warriors: Age of Imprisonment that I haven't seen, which means the fandom at large considers it unlikely and unsupported.
Still, fwiw, as I think on the conjunction between the official statement that the story will be canon and a HW game's need for more playable characters than we currently have pinned down from
Tears of the Kingdom -- Zelda, Raru, Mineru, the four masked sages; Sonia until she's murdered; maybe Ganondorf and Twinrova -- the more I suspect that the Ancient Hero (
this guy) will be there. Like many, I suspect that he's part Zonai. A question is whether he's also part Hylian or part Gerudo or both (red hair always makes fans suspect Gerudo lineage, e.g. Malon, Groose) or whether he's part of that lost frog-like people seen only in statuary.
But as he is from 10,000 years before BotW/TotK canon, he can't be native to Raru's and Sonia's Founding Era, which is much further back. He can't be their son. (Separate theory: We could be getting their adult children in this game, as new characters.) He could be a descendant of theirs. He could be the Eighth Heroine of Gerudo legend (speculated by fans to have been male). And... he could have gotten to their era by the power of the Zelda of his own era, who could even have accompanied him, adding two to the playable line-up.
Or he could actually be their adult son, who gets catapulted to 10,000 years ago
from the Founding Era by our Zelda in the course of the game.
Officially pronouncing this story to be canon, TPTB limited the possibilities for timey-wimey shenanigans messing with the story we know, but left them wide open for the stories we don't know.