Michael Jackson stayed black??

I don't think you can keep him black without seriously altering his genes. At which point, you don't have Michael Jackson at all.

However, let's take the latter half of the idea. Let's say Jackson is never, for whatever reason, accused of child abuse.

I still think there would have been a decline in popularity. It wouldn't have been quite as steep, and there certainly wouldn't have been the kind of revulsion towards him as there was before his death, but he would not be as popular as he was in the eighties.

Not sure about that. While its true there WAS a backlash towards "80s" music around the 90s, he could have followed the paths of Madonna and U2 and stayed relevant through the decade. Of course, he'd have to tone down the bombast (less outrageously expensive videos for one).
 
The clearer issue was to have him avoid getting burnt by the Pepsi commercial, which led to his addiction to painkillers. Get that out, and he'd likely still be alive.
 
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