In the last scene of Mission Impossible: Ghost Protocol, after Ethan tells William that Julia is alive, Ethan prefers to have a look of Julia only from the distance. While Julia after finding that Ethan is there and he is looking at her, does not prefer to meet him and they just give a smile to each other and then Julia steps into a shop leaving Ethan behind. Why do they not meet each other?
First Julia waves bye to Ethan before going in to shop. Second, as far as I think, they both have chosen to stay separated for Julia's safety. Also Ethan only tells the secret to William to clear the misunderstanding, not any other member of his team. If they meet, it might have possible that MI agency or someone else might find her.