Souma now a Elite 10 after beating Eizan?
Each side must lay out their "compensation", or something they must give up if they were to lose the challenge. Both sides must agree that the compensation of the duel equate with each other.


http://shokugekinosoma.wikia.com/wiki/Shokugeki

I guess the battle will only save the polar star dorm. Originally, whatever they bet before the Shokugeki is what they'll get when they win. This means if Souma wants to dethrone him, he'll need to propose another battle asking for the position if he wins.

But we'll see on the next chapter what would be the outcome.