Nomura's call, my friend.
I think that the only two Org. members that might actually come back as whole people in KH3 are Xemnas and Axel. Xemnas because he's an incarnation of Xehanort and Axel because... well, I can see Nomura buckling under the mere pressure of fans.
eh i think we will end up seeing Axel's heartless somewhere =D