From Odo Itals's thread
Captain Pike goes aboard the Romulan ship, Spock is left in command, and Kirk leads the mission to destroy the weapon [...].
And this is where big changes start, separating this movie’s reality from the rest of the franchise. Nero, the leader of the Romulans from the future, has created an alternate reality. A point that is hit over the head a few times, by Spock & Uhura, by Ambassador Spock to young Kirk....
Obviously, the alternate reality has NOTHING to do with the design changes, because it happens well after the newly designed ship, bridge, uniforms etc. are shown to us but is rather a vehicle to make future changes possible.
I would like that (I hate the idea of this being some "ENT sequel")
It also would seem that the design changes might not be explained in any way. Good.
Seems it's a remake AND a reboot after all. w00t
it would also mean that Kirk's backstory is the way "it was supposed to happen", even in the old timeline.