Michael Jackson owes Sony and Epic Label Records.. He doesn't care about money, but his fans. Fans overcome his profit, therefore he would not have any voice impersonators to replace him, just to finish an album.
There may be people that had duets with him, and finishing something, since he mostly finished raw recordings (demo). But when it comes to music, face to face with Michael, I am sure Teddy Riley knows more about the truth that a family that loves to manipulate unsure people, and especially media.