Marvel Studios’ head Kevin Feige has revealed that Thanos, who was portrayed by actor Damion Poitier in a brief closing credits cameo in The Avengers, will be making an appearance in Guardians of the Galaxy in which he will be portrayed by a real actor.  Director James Gunn confirmed that Thanos would appear in Guardians (see "Geek Film News Round-Up"), and now Feige has confirmed that the supervillain will be portrayed by an actor and the role has been cast, saying "There is an actor, I’m not sure we want to announce it yet."
Feige told Empire Magazine that Guardians was going to be something of a departure for the MCU: "Guardians will feel and seem the most separate.  But in a summer where people are going to see a lot of sequels, some of which are ours, and a lot of reboots and familiar faces, we were excited about the idea of bringing something new and totally unexpected to the screen."