I think the estate cannot release them without permission from Will I Am, the same way reminding Queen members had to get the estate's approval for releasing Freddie and MJ duet.
Will was deadly against any posthumous albums and thought it was disrespectful thing to do, but as time has passed, he has softened his opinion, so who knows?
This is what he said earlier:
Earlier this year, Will talked to Access Hollywood about some of the songs he recorded with Michael, mentioning “Dreaming,” “Still the King,” and a James Brown tribute called “I Will Miss You.” But he still maintains that none of them will ever be released, because Jackson didn’t give them a final okay. “
He kept his vocals and I kept the music,” he says. “We had that understanding.”
Seemingly they had more than those 3 songs mentioned above paragraph, as I found this:
will.i.am recently opened up that he and Michael Jackson have cooked up materials for the late singer's new album. "It was going to be out of this world. It's something Michael has never done before - a dance music album. I was very proud of it," he told Daily Mirror.
"He was very protective and kept it under lock and key," the Black Eyed Peas' member explained further. "After we made it I had to hand back every demo. He was a perfectionist and didn't want anyone to hear it until it was ready."
Unfortunately, will.i.am is not sure whether the album will be released or not since it hasn't been finalized when Michael passed away on June 25.
Furthermore, will.i.am told BBC at Glastonbury Music Festival this weekend that the new materials were kept by Michael. "He had all the hard drives because I didn't want to be responsible for that," he stated. "It's one thing to lose a Black Eyed Peas hard drive. I move around a lot and to make songs with Michael Jackson and risk me losing that music, I didn't want that responsibility. So he kept all the stuff that we worked on."
Read more:
http://www.aceshowbiz.com/news/view/00025404.html#ixzz30Fu0WAnZ