A couple weeks ago I've read somewhere else that the show's current timeline (season 4) could be a copy of the original timeline, which is out there somewhere; so Peter missed the original and fell into this copy, where everything seems to be the same but it's so different underneath. What do you think?

I love speculations – this is the moment when our imagination can go wild. It might be true what you are saying, Mr.Linc, that it’s a copy of the original timeline; also, it might be a third Universe (although I doubt it, it would be a too simple explanation); it might be something that didn’t even cross our minds – after all, it’s Fringe we are talking about, so everything is possible.