I actually believe it's more possible now than it was before. They have a formula to do it and take very little effort as well.
It all starts with just reusing songs from The Ultimate Collection, which just has to be sacrificed. It's kind of a misnomer release, anyway. (It doesn't have every song in his discography but it's the Ultimate? Really. Anyway)
I think long term the Estates plans are to put out certain songs, demoes, and rarities on anniversary rereleases, and put the best, most vocally complete material out on as many posthumous albums as possible.
Bad 40/50, for example, would just include Scared of the Moon and Cheater. Dangerous would include Someone Put Your Hand Out and as much special edition stuff as they could. Invincible would include Shout for sure. (Streetwalker, by Estate logic as well.) And We've Had Enough, Beautiful Girl, etc.
Hot Street is being saved for either a new album or Thriller 50, Nightline definitely is going on Thriller 50.
Other songs like Chicago 1945, Buffalo Bill, and everything that slots in between albums, could potentially make it to regular albums. Since they don't have really much that qualifies as the follow up to Invincible anyway.
HIStory would be the hardest release, but they'll find a way, just by releasing early demoes, the few outtakes that are, and maybe some other song that has no place being there. Probably overlap with Blood on the Dance Floor too.
Once they've exhausted enough songs in that way, eventually a comprehensive box set with every song put out ever, would become the next Ultimate Collection. And the new anthology they could make would include songs that basically aren't complete at all. Basically just sketches. Probably with demoes and alt takes of his classics as well. They could take us from Don't Stop Til You Get Enough to the 2008 Best of Joy.
Ultimately with that formula they could call it a day. It's literally the lowest effort imaginable. Yet they still might not do it. But this is probably how, so bare with it.