According to the guys over at TrekMovie.com, they have stated that the photos below were taken on the same day as the photos earlier released containing Zachary Quinto as Spock, and were from the same source as well.
Pine’s Kirk can be seen wearing the same uniform as Quinto’s Spock so this appears to confirm that the black shirt and grey pants is a new uniform variant (or at least part of one) for the new movie. The shirt is the same one Pine’s Kirk wore for much of the 2009 Star Trek movie and is actually the shirt worn under the regular gold, blue and red tunics. Those standard uniforms will also be worn in the Star Trek sequel so this version with the grey slacks and without the tunic could just be a variant for certain situations.
Starring Chris Pine, Zachary Quinto, Benedict Cumberbatch, Karl Urban, Zoe Saldana, Simon Pegg and Alice Eve, The much-anticipated Star Trek sequel is slated to hit theaters May 17th, 2013.