Cotto will vacate, and Golovkin's next opponent will be highly ranked by the WBC (Heiland for instance) to upgrade his interim to full world title.
imagine if they just downgraded Cotto instead of stripping him. Could possibly get a few more sanctioning fees
If Cotto fights Heiland, expect a new WBC/Ring champ and Heiland-GGG fight to get made around Sept for WBA/WBC/Ring titles.