As I outlined above, both USC and Oregon State benefit from the PAC 12, so what does USC do? They can threaten to go independent, but the PAC 12 presidents are smarter than me, they know that USC will lose money as an independent, when compared to the PAC 12 deal. So they'll call USC's bluff. USC might still go independent, costing both themselves and the PAC 12 money, but it's unlikely, and USC won't be able to convince WSU and OSU and Utah and Arizona to vote themselves less money (and it would require a unanimous vote, so that's not happening without a stick, and USC doesn't have one).
Now maybe I'm wrong. Maybe ESPN is willing to pay $20 million a year to the PAC 12, but they'd pay USC $25 million a year on their own. If that's true then USC has a stick and they can force the Cals and Utahs and WSU's of the world to vote for unequal revenue sharing, because USC has someplace to go. But unless independence (or super conferences) is going to make more money, USC won't be able to get the votes.