I was watching the trailer and noticed something. It appears that Darth Vader is actually in the Trailer.
He appears in last frame of Obi-Wan on Coruscant going after the Bounty Hunter (just before the clone children). It appears on the right side of him on the building. It is really noticable if you can download the large version. If you watch Obi's expression in the whole sequence it looks like he is actually reacting to the image.