I don't think it would be a good idea to end the first movie with the allegations. People who watch the first part won't necessarily go to watch the second part and they would just leave with the impression that he was guilty. Whether they decide to bring up the allegations in the first part or in the second part, they need to fully deal with the allegations in the same movie, you don't want to raise up questions without providing answers.
They could end the first movie with Bad and show how the media was beginning to torment him, hinting that things are about to get rough in the second part. Ending it with Bad would allow them to start the second movie on a high note with Dangerous and the Superbowl before the allegations hit.
Remember that sad letter that Michael wrote in his hotel room during the Bad tour? That could be a good moment to end the first part, the last sentence hits pretty hard:
“Like the old Indian proverb says, “Do not judge a man until you’ve walked two moons in his moccasins.” Most people don’t know me. That is why they write such things... I cry very, very often because it hurts and I worry about the children, all my children all over the world. I live for them... Animals strike not from malice, but because they want to live. It is the same with those who criticize. They desire our blood, not our pain. But still I must achieve. I must seek truth in all things. I must endure for the power I was sent forth, for the world, for the children. But have mercy, for I’ve been bleeding a long time now.”