It was a revelation to see Thanos smiling at the end of The Avengers. Many fans knew what it meant to see the Mad Titan as the villain behind the Chitauri invasion upon the Earth.
For a while it was Kevin Feige, president of Marvel Studios, who said that Thanos would be appearing in the 2014 Guardians of the Galaxy movie. So far actor Scott Porter talked about his love for Marvel Cosmic and his desire to play Nova or another Marvel Cosmic character.
Feige has only said that Thanos is in the movie, however he recently informed that the Mad Titan Thanos will also appear in The Avengers 2 as well. James Gunn has appointed as the director for Guardians of the Galaxy.
Jim Starlin, the creator of Thanos in the Marvel universe also stated the appearance of his creation in the upcoming movie Guardians of the Galaxy (2014) and The Avengers 2 (2015).