This really isn't hard to understand.. The prophecy made was of a blue-eyed boy who will change the world. Clearly that is Naruto. Sasuke isn't being entrusted with the prophecy to save the world like Naruto is. Sasuke is being entrusted with the sage's power which is two completely different things. The sage didn't know how Indra would react after entrusting Ashura and that's how this whole thing started. This time he wants to entrust Sasuke (Indra's successor) with his power and see how Ashura (Naruto) would react and which way the ninja world goes on from there. That is why he asked Naruto what will he seek after the battle is over...