Clue 1 - A gem, specifically the soul gem.
Clue 2 - A hint towards Vance Astro.
Clue 3 - A hint towards the story-line, how many of those characters fought against Thanos during the gauntlet shenanigans.
Clue 4 - It's not so on the nose, It's not so on Thanos! What was not on Thanos in The Avengers.
He said he was dropping some plot, so here's my theory that will probably be disproved in less than a day. GOTG begins in the past, with a quick montage of Vance Astro going into Project: Starjump<--wikipedia. His ship encounters Thanos who badly damages it bringing Astro out cryo-sleep and into the present. He escapes and meets the GOTG and explains his situation and they tell him they're actually running from Thanos too, because they have the soul gem. So they'd really be chased by Thanos, various bounty hunters, and Adam Warlock who only wants the gem with someone who won't abuse its powers. The movie would mainly focus on the Guardians, with scenes featuring, Cosmo and the Head/Space Station, Thanos, and Warlock with some hints of his other self thrown in at the end.