We already have a singular pronoun in modern English: it. If people want to they could stop using gendered pronouns and just use “it” . The practice of using “it” to refer to humans is quite common in other languages, including Mandarin. Seems to work fine. I live in Asia and Chinese speaking broken English often refer to people as it. We all just roll with it.
Unfortunately for non-binary people, this pronoun thing will not catch on outside of their circle of friends. Just not enough people care and there probably never will be enough. When have the masses ever changed for the benefit of the few — very few in this case. We went to war to end slavery and that was a lot more people and a lot more oppression.
I’m not non-binary, but if I was I don’t think I would mind people using the pronoun corresponding to how I presented as on any particular day. And if someone isn’t sure how I present, then they can use whatever pronoun they like. I’d be neither or both or whatever, so why should I care. I know non-binary people who enjoy seeing how strangers refer to them on any particular day.
Meanwhile, if someone tells me their pronoun, I will use it to be nice. But, I just think it is a losing battle.
My convention when I’m not confident of the pronoun to use is just to ask, “how should I address you”? If they say “Jack or Mary” I know. If they use a name that could be male or female gender, my question is their opening to tell me their pronoun. I’ve seen people get offended by being asked their pronoun, as in “I’m obviously a fucking women you asshole” as an answer. This is another reason I wish we could all settle on “it”.
Oh, and to actually asked someone their “preferred” pronoun can also be highly offensive to some people, in case you didn’t know. It is not preferred, it just IS the right pronoun. To say “preferred” implies the speaker has a choice or is doing them a favor or courtesy by using the right pronoun. A cis-man might rightly be offended if referred to as a she, so their you go. Same for everyone.
Can we all just use “it”? I won’t hold my breath.