@Richard76, unfortunately there is a technical problem when an artist dies.
From that point on, it is the Estate that decides the songs and albums that they are getting a release, not the deceased artist.
The Estate also decides the type of the released music (demos, finished music, partially finished music, etc).
The Michael Jackson Estate also already clarified another thing.
"
If we released demos by themselves, they would not be commercially successful because they are, by definition, unfinished" (The Michael Jackson Estate)
The Michael Jackson Estate is a company that, first and foremost, has to make profits in order to continue to be viable, so they are not going to release such stuff.
@mind&magic, in case of a physical release, pressing CD blanks occupies only a small amount of the overall budget.
The obstacle in a digital only album release (demo album or an album with complete tracks) is that there are some drawbacks.
For instance, a digital only album cannot sell well because listeners tend to buy certain songs from that album, rather than buying the entire digital only album.
Also, in case of streaming services, a rather significant part of the total revenue earned per stream goes to the streaming platform itself, which makes the digital release not really profitable for the Estate or for the artist.