Star Wars: Rogue One Teaser Breakdown - 25 Things You Need To See
2. Jyn Goes Imperial
Lucasfilm
"What will you become?" says Whitaker in voiceover as we see Jyn decked out in black Imperial get-up. A haunting end to the trailer, this really plays up the moral ambiguity behind the motivations and goals of the film's characters, something I hope gets explored deeper in the finished product.
As for what we're really seeing here, I'm tempted to say misdirect - Jyn is probably pulling a Luke and Han (although technically this predates them) and posing as an Imperial to get inside some base.
The disguise is most likely that of TIE Pilot sans breathing apparatus - the belt buckle and chest piece match up damn near perfectly - which could point towards an aerial action sequence or a scene of her sneaking in using one of the space fighters. There is a small chance it's Shadow Trooper gear without the arm armour, which would make sense given their prominence in the film, although there's no good enough comparison to confirm (or deny) that.
Oh, and if you're wondering what those two things sticking out of the back are, they're the blasters she's running with in the previous AT-AT shot (placing this around that set-piece).