Keep in mind that the Estate may intentionally hold back information about the existence of more unreleased songs (in the vaults) in order to lower fans' pressure towards the Estate for releasing more posthumous albums with such stuff.
In any case, certain sources spoke about the number of the singer's unreleased songs.
For example, Tommy Mottola stated at one point that there are dozens and dozens of songs that did not end up on Michael Jackson's studio albums.
Tommy Mottola implies that these songs were fully completed.
Teddy Riley also spoke about a lot of finished tracks that were considered for inclusion on the 'Dangerous' album.
Also, a possible 'Dangerous' anniversary album filled with Bryan Loren unreleased tracks would not be commercially successful.
This seems to explain why the Estate does not care about contacting Bryan Loren for such a possible project.
Also, do not rely so much on things that sound engineer Michael Durham Prince has said over the years regarding unreleased songs.
Michael Durham Prince is not really a reliable source when it comes to unreleased songs.
For example, when he was asked, he had no recollection of the existence of outtakes from the 'Invincible' album (such as, the 'Can't Get Your Weight Off Of Me' outtake).
