WBO #1 - WBA #4 - IBF #10 Denis Boytsiv RUS WBO #2 - WBA #- - IBF #15 Seth Mitchell USA WBO #3 - WBA #3 - IBF #6 Alexander Ustinov RUS WBO #4 - WBA #8 - IBF #9 Chris Arreola USA IBF is holding a mini tournament between Adamek-Walker-Solis-Pulev WBA doesnt really count due to super champ bull****
It could be any of those guys. Though less deserving then the above 3, Solis presents more of a potential challenge. I can't fault Wlad if he fights Solis cause its a good scalp and there's some intrigue since Solis was doing ok in that first round with Vitali. If Wlad won't rematch Haye and Povetkin and Pulev won't fight him, then Solis might be the best opponent.
Hopefully Arreola but Arreola is gonna fight Stiverne for WBC eliminator so I have no clue. Maybe Wach.
The poster who would know is Simply the best that guy is dialed in to the K2 camp i think he would know