No, it hasn't.
I think you find time trave lin TREK pretty much states the future is different when the past is changed. STAR TREK has never once stated it uses the theory that altering time creates a second spereate universe its always done the prime universe is changed.
actually one of the theories of the mirror universe was it was a divergent universe at some point past in history.
and we saw the other parallel universes in tng parallel episode/
so no this isnt new.
Two universes being similar or even identical up to a certain point in time, and after that diverging, doesn't mean they were one universe up to that divergence.
STAR TREK has never presented changing the past as a way to create new universes. It's a way to CHANGE that one existing universs.
You can't change the rules midstream. If it was a simple fact of physics, temporal mechanics, or whatever in the TREK universe YESTERDAY, it's going to still be part of the laws of that universe TOMORROW.
If the movie DOES take place in the past of the known Trek universe (for the most part..it'd be the FUTURE of ST:ENT), then this movie has seen that timeline CHANGED.
The only possible out for this is the idea that the movie actually takes place in a parallel universe, and this is what I suspect.
If Nero and Spock are from the original universe and somehow crossed over when they went into the past, fine, but there's indications the Kelvin was NOT in the main universe when Nero arrived.
The Kelvin tech looked more advanced than that on Pike's Enterprise, which wasn't supposed to exist for a number of years yet.
The communicators seen used by Kelvin crew members were at least externally identical to those used on TOS.
Pike's crew used communicators that were VERY different. The TOS type shouldn't have shown up until sometime after the time period of THE CAGE.
WHY would the Kelvin crew have them so early?
The look of their tech is just plain WRONG, and I suspect this means the movie takes place in a similar but different universe, a universe which has just been made even more different by Nero's messing with its timeline.
Again, I don't know if Nero and Spock are from the future of this new unvierse, or from the original one, and at this point I don't really care.
The changing of the past of the original universe would have meant it was totally changed, not that an offshoot timeline had formed. The original would be getting overwritten. (See the time-travel episodes of TOS, TNG, AND DS9 for proof on how it works in the TREK universe.)
This means that the movie either is the new version of the original universe, or that it's been an alternate one all along.
I suspect the latter, for reasons already described.
The original timeline likely remains, not because this is "only an offshoot", but because it was and is a parallel universe, and now we get to watch Star Trek start all over again in a universe we've never seen before, with who knows how many differences.