Obviously everybody doesnt kno if oro's intentions or as he says. If he is plotting something, it would most likely be enhancing sasuke's ability possibly rinnegan, to take his body. I remeber sasuke "finishing" Oro with a tech genjutsu, so Oro may still hold that against him. Although i think he doesnt have a cause to stay evil, being he could have destroyed the village and it just seems with how everything turned out that he doesnt have anthing to have a real resolve for anymore. I mean if he gets sasuke's body with rinnegan, perfect sussano, or what ever, I dont see what cause he whould use that power for at this point.