I do notice that Simon Pegg's name isn't listed in the cast credits of the poster. Odd. But that by itself isn't necessarily evidence that the poster is a fake. There are some movie posters here and there where the entire lead cast isn't listed so they can leave enough space to include the guest stars' names.
But there are other telling oddities. There's no credit for composer Michael Giacchino or costume designer Michael Kaplan, as there was in the previous film's poster, and the credit for DP Dan Mindel is right before the director credit. There's a credit for one of the two co-producers, Tommy Gormley, but not the other, and co-producers generally don't get listed on the poster. There's also apparently a credit for someone named Ben Burman, and IMDb lists nobody of that name associated with the film; maybe the creator of the poster meant Ben Burtt, or the first film's prosthetic makeup designer Barney Burman. Also, the opening line should probably say "PARAMOUNT PICTURES and SKYDANCE PRODUCTIONS present a BAD ROBOT production." The 2009 film listed Paramount and Spyglass, its production partner on that, and Mission: Impossible: Ghost Protocol
, also a co-production with Skydance, listed their name at the start of the credits.
And most importantly, there's no "Based upon STAR TREK created by Gene Roddenberry" credit.
So yeah, I think we can safely cue Senator Vreenak: "It's a faaaake!" Or at best it's a rough draft that got released prematurely before the kinks were worked out, but I doubt it.