The film will reportedly center around either Star Lord (per CBM) or Major Victory (per other online speculation) as he takes the lead of the cosmic team, with both Production Weekly and It's On the Grid sharing a log line that describes the film as "A U.S. pilot who ends up in space in the middle of a universal conflict and goes on the run with futuristic ex-cons who have something everyone wants."
What could they have? Well, it's anyone's guess but the smart money is likely on either the Infinity Gauntlet or pieces thereof. How that might come to pass, when the last time anyone saw it was in Odin's armory, may well be a question for Thor: The Dark World to answer.
Guardians of the Galaxy doesn't yet have a director or any stars attached (at least as far as anyone knows) but is eyeing a release date of August 2014.