After all the trash talk they did before the second fight De La Hoya won’t treat them well. Now Canelo is the champion and the third fight is more important for GGG. Canelo can make 15-20 million with lower class opponents too. GGG gonna be 37 next spring, to make the third fight as soon as possible is important for him. I can imagine they have to go back 70/30 money split, and zero requests about the judges, gloves, etc.
Obviously … In fact, the way the business works, Golovkin would be fortunate to get 30% for an immediate / May 2019 third fight. About judges, gloves, this is with the commission and Golovkin still has significant public backing so I don't think that is affected much. But money? Definitely, and probably more than you stated. What's probably going to happen (here I speculate) is that they go their separate ways for a bit, Canelo mulches Lemieux, Munguia, … GGG knocks off Murata and perhaps one of the many weak champs / former champs at 168 (he can still beat De Gale, Truax, Fielding easily and probably even Groves and Uzcategui). Saunders/Andrade, Jacobs/Derevyanchenko, Charlo pose huge threats to either but I'm think that Canelo finds a way to put them off for a bit … say fighting each other first … and GGG now has no obligations to fight either, so he won't unless BJS offers good money. Then they meet for a third fight in which Golovkin gets about 30% and Canelo finally wins decisively.
I hope the negotiations bore on and on yet again with arguments over every last detail before GGG retires leaving Canelo to fight a GGG cardboard cutout. The cutout will win according to most of the watching audience, journalists and retired fighters, but Canelo will get a controversial decision nonetheless.