u get the dude wrong...as sasuke and itachi had their battle, oro nearly took sasukes (weak, nearly no chakra left...u remember?) body, but then was sealed by itachi via totsuka-blade.
(and that has not much to do with how oros immortality-tech works...)
so oro wont come back.
and according to your logic...we have a sasuke without a soul now (would still explain a few of his decisions ;-) )...coz this was the body which oros mind tried to overtake.and if it wasnt oro sealed back then....guess what?it had to be the only other soul in sasukes body at that time...