No. The original timeline was the first three seasons. Then Peter did his thing and disappeared from existence. The next season (last season) started without Peter -- he never existed. But then he came back (still no idea how or, better question -- from where) and still, nobody believed him, because for them he never existed. Slowly Olivia and Walter started remembering things. The child Observer made Walter remember even more. Of course the term "remember" doesn't really apply, as Walter (in this timeline) never lived through those experiences.