If someone could present a valid case for a "third gender" or whatever, I'd be willing to entertain the idea (hell, I'd love to see this). But every supposedly non-binary person I've seen just exists somewhere clearly between male and female, as just a mix of the two. Beards and dresses. Make-up and grease. That's not a continuum, that's scrap parts glued together into an identity. We already have a perfectly good word for this, androgynous, which clearly explains you're not on one of the polar opposites of gender expression. Show me that you have a valid reeeeson to be considered neither masculine nor feminine, not just a mix of the two, then we can talk.
I don't think this will happen before aliens.