You say that, but Link being a girl two games from now wouldn't really contradict canon, require explanation or even look all that different.
It's all the same to me honestly, but saying it can't stray is a bit weak.
Fair enough. It is.
My issue isn't even with future installments of Link being female, it's just trying to assign identities to existent iterations of him that have established character's and identity, like the OP asking why BOTW Link is still being viewed as a part of the binary despite the fact the creator stated he was, in fact, a part of the binary and in general the all-too-common trying to pull threads on many long-established and persistent, non-reincarnation characters like some people who want canonically straight characters to come out as gay despite the fact it conflicts with the character's established identity.
I'm a part of the LGBT community; I, myself, am bisexual (sorry for the people who think I'm biased against the LGBT community, I guess), but I don't personally believe in pressuring content creators to represent me if it is not in their will, and I do not believing in trying to assign identities to characters that simply do not exist in the canon. I'm bisexual, but I'd be perfectly comfortable with there literally never being a single bisexual character in gaming every if so should it be. I'm a content creator myself, and while I don't exclude minority groups, be it racial or the LGBT or religious, I also sometimes just don't write about African-American or LGBT characters, and I think I'm perfectly well within my rights to do so and I'd definitely hate to have nonstop discussion about why my main character isn't enby genderqueer just because I didn't write him as too overly masculine or her as too overly feminine.
Everybody who has ever had their hands on Link sees him as male, and everybody who has their hands on him now sees him as male. There is no Link with different gender identities, and BotW 2 Link will not be enby genderqueer, and trying to pull threads to explain why he is one of these things is honestly weird to me. And I genuinely don't think there ever HAS to be a genderqueer or gay or bisexual or female Link EVER, and I do think asking for anybody in charge of LoZ to include this is asking for too much. I genuinely do not believe in pressuring creators to touch upon subjects they do not want to if they do not want to because I would hate for people to do it to me.
It's fine to want more representation, but I will never pressure a creator to change what their vision for their character or world or story or game is unless there is some actual genuine issue with their storytelling or the gameplay is actually objectively busted. The creator's vision for Link is clearly that of a boy. Leave it be.