i think it really depends on Sasuke. i dont think he'd be able to kill her. he may end up fighting her but it wont go as far as actually killing her. remember he said he doesnt kill people for no reason and there's no reason for him to kill Sakura. you never kno, maybe her words will get to him somehow, they did back then before he left Konoha. if they didn't, then he wouldnt have said "Thank you" in a gentle way. i think he cares for her deep down, its just that his darkness takes over him and he cant control it.