If we brush away all of the politics, my point is that linguistically there is already a precedent for using "they" in singular form. Don't misinterpret my position on the matter. I find it annoying and I really struggle to use "they" even when someone specifically tells me to use it. That leads to my second point. Despite all of the pushback it's already becoming commonplace. I'm not sure I'll ever be comfortable with it, but my opinions don't mean jack. The only thing we can count on is that things can and will change.The use of "they" is limited to very few situations, mostly predicated on the saying that can denote a number of people in case there are more than 1. Or if the sex of the person is unknown due to lack of information.
"Are they coming", "where are they" are phrases that many use to refer to a group or a single person. It is used so commonly because the understanding by the recipient understands the reasoning. Just like "hey guys" can mean a group of guys or just a group of people, even if there are women present.