It's not going to happen until he has all the belts held by his own stable of promoted fighters. When Vitali Klitschko was the champion, King had Ruiz, Brewster and Byrd. Did he have them fight to unify any of the titles then? No, because he knew the only belt that mattered was the one Klitschko had. Why would he risk unifying the titles he controlled just to lose them in a final unification bout with Klitschko (King knew that Klitschko would have beaten any of the other three ... why do you think he pushed for Rahman to face him?). King is always pushing for unification, but it's not realistic unless he can promote the linear champion AND the challenger with the title to unify with. He would rather have all of the titles in his grasp to then promote a tournament (something he's always hinted at) between those four fighters (Fighter A vs. Fighter B and Fighter C vs. Fighter D with the final fight being between the winners of those two fights). Then the losers can battle it out for the WBA title that will be stripped from the undisputed heavyweight champion.