Seems Shumenov is now working with GBP and will be on the Broner-Madaina undercard, most likely against Tamas Kovacs. Seems the fight will be on regular Showtime and will air before the ppv broadcast starts.
You could be right. I'm not sure GBP would be messing with Shumenov unless they had future plans for him and Hopkins is one of the only major guys they have at 175.