I was rewatching the Season 5 premiere episode again and in it Daniel says something along the lines of time is like a string. You can move forward on that string and back, but you can't create a new string. In the same episode he tells Desmond that he is special and the rules don't apply to him. So with all these alt. timeline theories being thrown around, I'd say it is possible, but it requires Desmond. I think the result of Jughead will be a combo of WHH and ALT. I do think also that the first scene of season 6 could very well be the first scene of season 1 but with slight varriations.