J.J. Abrams has repeatedly emphasized the importance of the international market in selling STAR TREK INTO DARKNESS, so it's hardly surprising that the latest major press event for the upcoming film was held in Sao Paulo, Brazil. What is surprising is that they gave away the identity of Peter Weller's character so close to the film's release.
You shouldn't even be in this article if you're worried about spoilers, so this is your last chance. To be nice, I'll place the reveal after this here video...
Peter Weller plays Admiral Marcus, the father of Carol Marcus.
There are some other interesting details in TrekMovie's reading of the report out of Sao Paulo...
1) The order of sequences at the beginning of STAR TREK INTO DARKNESS has been changed. If you saw the IMAX preview, the film opened at the hospital with the introduction of John Harrison (Benedict Cumberbatch), followed by the Nibiru Volcano sequence (concluding with Spock about to be consumed by lava). This has now been flipped: the movie opens with the Nibiru sequence, title card, then the hospital.
2) On Nibiru, Kirk has a choice to make: violate the Prime Directive by surfacing the submerged Enterprise in order to save Spock, or stay submerged and let the Vulcan die. Of course he violates the Prime Directive, and of course...
3) ... he is demoted by Pike, who would like to send Kirk back to the Academy. Admiral Marcus either convinces or orders Pike to retain Kirk, so Pike takes command of the Enterprise with Kirk as his first officer. Spock is moved to another ship.
4) Pike is injured during an attack on an emergency meeting of Starfleet (which follows the attack on London).
5) Spock at one point orders an evacuation of a crippled Enterprise as it plummets to Earth.
6) There's also a foot chase between Spock and Harrison in San Francisco. Eventually, they fight.
7) And, not for nothing, there's a scene where Kirk and Spock are in Engineering struggling to stabilize the ship.
If you're fluent in Portuguese, you can read the whole report (and maybe flesh out details in the talkback; I ain't gonna stop you). I can't tell from either write-up whether they revel the true nature of Marcus's character. If so, that's a pretty big spoiler. As for Harrison = Khan, that's still unclear. Officially.
Based on what I know, Abrams and company are running out of reveals.