Yep. I'm one of the few people that has heard it, because someone involved with the track played it for me. I don't want to break trust and say exactly who, but not only did they play me the song, they played it from the multitrack session and isolated Michael's vocal and some of the instruments.
It's astoundingly good.
Now, as far as it coming out? D'Angelo Estate might have a hard time with that. My understanding is that Epic and the MJ Estate own the rights, because it was commissioned for the "Xscape" album, and didn't make the cut.
From what I was told, there was a disagreement about whether Mary J was the right person to be on it, with at least one stakeholder suggesting she be replaced with a different female singer (I also know who the replacement suggestion was, and frankly I think Mary is a better choice and did a stellar job).
My guess is, unless a LOT of money changes hands, Branca and Epic aren't going to let that one go so easily. This ain't like the Drake/Don't Matter To Me situation, and that one cost Drake a lot of money to get it, too.