Its hard to tell with Kojima. I don't believe its a "preview of a remake" just something from MGS4, either a flaskback or more likely in game footage of Snake returning to Shadow Moses. As for the controversy due to it being "young Snake" remember that Kojima has a history of screwing with his fans head and is willing to change around scenes in order to create misdirection (remember MGS2 footage that was altered to hide Raiden). Its all up in the air, really and we'll know the truth in June.