I , too, think the universe depicted in Trek 09 and Into Darkness, is a parallel universe from the beginning. Long before Nero's incursion. It's one of the countless universes in Trek (as seen in Parallels, TNG). With similar, but different, people.
It solves the continuity issues people have with the new films
However, I think Enterprise is in the same universe as TOS, TAS, the movies 1-10, and TNG, DS9, and VOY. First Contact didn't affect the timeline. The NX-01 was always called Enterprise.