Quillin's supposedly in the last fight of his GB contract. After that he could move into Mayweather's stable. It's all in Oscar's best interest to get a money fight with GGG than roll the dice with Korobov for less than half the money. Might be able to convince Haymon to go along with it if Golovkin agrees to fight Lara after Quillin, because Lara's going to have a hell of a time getting another meaningful payday. With another situation where all of Golovkin's ideal opponents are looking tied up with other fights (Chavez/Froch, Cotto, Soliman, Alvarez), HBO might feel the pressure for this one, especially in light of the poor ratings (which had as much to do with seasonality as it did with a non-American fighter in Geale).
GGG has no reason to move out of MW. He could rule it for years and become an ATG while even having 168lb title simultaneously. This BS about GGG having to move up is mindless babble.