I'm a big Golovkin fan & I agree with DiBella - Golovkin needs to generate some name recognition in the states & beat a couple of the other major fighters.
Mathew Macklin is the most likely next opponent for Golovkin, as HBO featured both of them on cards, & would likely be a great fight.
Then hopefully either Geale, Pirog, or the winner of N'Jikam vs Quillan.
Martin Murray is another good, credible opponent with some name recognition due to his draw with Sturm, & is looking for a big fight.
But the important thing for Golovkin is stay busy & not get stuck on the shelf by HBO waiting for the big fight.