It's because of Expo 2017 being held in Kazakhstan for the first time ever - the event lasts about 4 months and millions of people will attend as it's the first one ever in central Asia.
Golovkin has said a few times he'd love to fight in his home country during it and give his home fans a big show

He's made no secret that he wants to Unify so this surely will happen plus BJS/Warren will be ringside in New York and are making their announcement of Saunders next opponent then - obviously the winner of GGG v Jacobs.