Well, like others I don't think it will ever be anything more than a universally accepted colloquialism. I've used it myself, whereas I have never used "y'all", even though I am very used to hearing it used.

I think we do want the plural better defined, no argument. I don't know if we need the distinction as made in Indonesian. I have been known, however, to say "you, singular" and "you, plural" when I want what I say to be exquisitely clear ...