I interviewed Orianthi who was MJ's guitarist in the band for his 02 shows, and she spent q few weeks in rehearsal with him before his death.
According to her, he was very healthy, very bright, rehearsing hard every day, and showing no signs of any physical illness, so maybe he would have surprised his detractors.
At least - unlike all the media speculators - she knew him personally and worked with him on a daily basis, so her opinion certainly counts for something.