Warning: Spoilers Ahead!
I have a theory about the J.J. Abrams Star Trek universe. It’s likely wrong, because Abrams seems pretty well content to just do whatever he wants regardless of whether or not it makes any kind of sense (see : The Enterprise at the bottom of an ocean), but it’s a theory I have nonetheless.
The Abrams Trek universe is actually an alternate Mirror Universe.
What follows is a whole bunch evidence that demonstrates, beyond a shadow of a doubt, that I spend far too much time thinking about this kind of shit. Some of what follows here isn’t necessarily canon, but it’s the best info we have so I’m going to go with it.
The whole point of the Mirror universe was that it was supposed to demonstrate the Butterfly effect. For those of you who aren’t familiar with it, the premise is that one small, seemingly insignificant change can lead to considerably larger (and seemingly unconnected) changes down the line. The Empire of the Mirror Universe was supposed to be what would have happened in the Trek universe had one small thing changed somewhere in the past.
That small thing, according to the novels by William Shatner (along with Judith and Garfield Reeves-Stevens), came in the aftermath of the events of Star Trek: First Contact. According to them, the memory wipe that Beverly Crusher performed on Zefram Cochrane did not take, and he had full recollection of the events of the film (namely that Earth was attacked by The Borg). He had to decide whether or not to tell others what happened. In “our” Trek universe he chose not to, and Starfleet ended up being a peaceful organization. In the Mirror Universe he shared what he knew, and The Empire was born (this was all pretty much made canon in Enterprise, where it was confirmed that Cochrane remembered the Borg attack and we saw what happened during first contact with the Vulcans in the Mirror Universe).
The upshot of all of this is that the Mirror Universe was the result of a major attack on Earth during a crucial stage in human history.
In the Abrams Trek universe we have something very similar happening. When Nero came back in time he destroyed the Vulcan homeworld and came fairly close to destroying Earth as well. In the “known” Trek universe the Earth was not threatened to that level until considerably later (I may be wrong in this, but it really wasn’t until the events of Star Trek IV, and in that case the threat wasn’t really a military one but more of a misunderstanding). Starfleet kinda freaked out after this, and started looking for ways to increase their military strength. This caused them to seek out Khan, who had the know-how to help them build powerful military class starships that could be manned by small crews.
You know…like the ones in the Mirror Universe.
So what happened? Earth got attacked AGAIN, and this time the damage was much worse. Thousands of people killed, not to mention the destruction of the command center for Section 31 (The shady spy organization of the Trek universe). While Commander Marcus was clearly a major player in the whole military push in Starfleet, it’s highly unlikely he was able to divert that many resources to building the Vengeance without the rest of Starfleet Command knowing about it. The plans for those kind of star ships exist, and Earth has dealt with two major threats in just a few short years. On top of all of THAT, the events that happened on Kronos are likely to spark an all-out war with the Klingon Empire (in contrast to the Cold War parallel that existed in the known Trek universe).
When you take all of this into account, it’s highly unlikely that the alternate Trek universe will revert back to the relatively peaceful calm of the known Trek canon. While the seeds of The Empire were planted a few hundred years later, they are still there, and they will continue to grow. This isn’t likely to result in quite the same Empire we saw in the existing Mirror Universe, but it certainly won’t be the Starfleet we know and love.
So…that’s my grand theory that I’ve spent far too much time hashing out in my head since I saw the film.
And this is my horribly anti-climactic end to my post.