I doubt Sauske's going to kill Oro...I mean, seriously, the main character is Naruto.
It'd be like Vegeta or Krillin killing Frieza instead of Goku...
But maybe it might happen.
I actually agree that it might not happen, but I want it too. Generally I think someone like kabuto will intervene, but sasuke hasnt showed orochimaru his true power; so it will be a good fight. I can't wait too see how it turns out, hopefully with orochimaru's death.
You forget, naruto may be the main character, that dosent mean he has to do all the killing. The sound 4 wasnt killed by him, nor was kimi. To think, he hasn't killed anyone of importance. I bet saskue kills oro and kabuto comes in to stop the fight. I still hope oro dies >.>
I bet saskueor oro has the 8 tailed demon, hence why i think oro left akatski. Akatski probably decided one day to target Bijuus and oro had a bijuu. It was run or die. (<--- i dont like to read spoilers so i might be wrong on that)