Miyamoto can say whatever he wants. The fact is they haven't treated link like an avatar, either inside the games or out. Hes been in non zelda games. Hes been in cartoons. Customization options are totally absent save for name entry. The hero storyline never leads anywhere except straight back to link.
If anything they've been moving towards giving link more personality, as in skyward sword.
What you're not seeing is that link serves as an avatar. But link, the character, supercedes that function in importance.
Nintendo statements say one thing. Their actions something else.
Ok.
In that case, Nintendo's actions show that Link is not a single person and rather multiple people embodying the same spirit. Like people have been saying. Their actions show that "Excuse Me Princess" is not the same guy as "Great I'll Grab My Stuff" who is not the same person as "I am in Love with Ilia" who's completely different from "Zelda is my Secret Childhood Crush and wtf is an Ilia".
So by that logic the next one could be a girl. Because they're different people anyway.