During The Anatomy of Superhero Film Music: Bringing a Comic Book to Life panel at Comic-Con, Avengers music supervisor Dave Jordan revealed that some sort of Guardians Of Galaxy preview would be part of the Marvel Studios panel.
While it was a little unclear what the preview might be, it could be anything from a cast panel to test footage to concept art. Several members of the Guardians Of The Galaxy cast are already at Comic-Con for other projects so it wouldn't be surprising if they also participated in a Guardians Of The Galaxy panel for Marvel Studios. We have heard that the Guardians Of The Galaxy production has been running a couple weeks behind, so it will be a surprise if the preview involves a completed trailer, but maybe there could be a showing of some early test footage.
The Guardians Of The Galaxy is scheduled to be released in movie theaters on August 1, 2014.