This is interesting because I too think that's the only single action that could clear Michael's name in the collective minds, because not even a fair trial did it. I'm not familiar with how American law works in this scenario, how long it takes for a "crime" of this kind to expire, but it's something that would be so good for the estate and the family, not to mention Michael's legacy, that I think they could agree to a deal of not suing him and not taking any other legal action if he did it. If anything, even helping him in the legal sphere.
The somewhat optimistic and somewhat pessimistic side is that I think it will happen someday, but likely only after his death or on his final days. Maybe through some book, memoir, video, letter... anything of the sort.
At this point, he likely learned how to live with this iron bag in his back forever. In his mind, he probably thinks that if he ever comes out and say it, it would be basically the same as admitting to killing Michael, because everyone knows that was the beginning of the end, the Pandora's box.