THERE ARE A BUNCH OF SITUATIONS WHERE "THEY" HAS ALWAYS WORKED PRETTY WELL AS A SINGULAR PRONOUN, AT LEAST COLLOQUIALLY.
THAT SAID, I STILL WOULD PREFER THERE TO BE A NEW WORD BECAUSE "THEY" IS REALLY AGENDER, RATHER THAN GENDERLESS. BUT ANYONE AGENDER SHOULD ALSO USE THE NEW ONE BECAUSE "THEY" IS ALSO TAKEN TO BE PLURAL. IT JUST SEEMS AWKWARD AND DEMEANING TO ME WHEN PEOPLE USE IT. BUT IF THEY WANT TO USE IT AS A SINGULAR, I DON'T REALLY MIND.