I know it's vacant right now at 122. It's supposed to be determined by a fight between the #1 and #2 guys in the division facing off, but the vacant belt has been on the line before when #1 and #3 guys face off -- Ward-Froch comes to mind as a recent example. Nishioka is ranked #1 and Donaire #3 by the RING, with Rigondeaux occupying the #2 spot. Does anyone know?
It should be according to Ring's new rules. I guess you'll find out soon enough unless there is a draw or no contest.