Me too, despite I always think that MJ is alive, I'm not so sure he will return.
I tell my possible reasons (some of them in agreement with yours):
He may have had a disease (of course I hope not) and, to heal, he needed quiet.
He "has gone", because maybe he wanted to "make free " his children, in fact now they are no longer walking with the mask and they go into public school (if the news are true).
Perhaps he thought it was time to retire himself from the scene, as other great artists did, and he chose this way: for example in my country, the most famous singer woman, at some point, decided to be seen no more, even no more photographed, but she continues to produce album.
Maybe he wanted to show that, with the past false accusations against him, it is as if he somehow "has been killed".
But I also think that he, somehow, will continue to act so that one feels his presence and, perhaps, if the conditions will be right, he could also return.... in the movie "This is it" he sang "... whether is love, I'll be there ".