"The general answer is yes," Kevin Feige said when asked whether Guardians of the Galaxy takes place at the same time as Marvel's other "Phase Two" movies, Iron Man 3, Thor: The Dark World and Captain America: The Winter Soldier. "It's not exactly revealed what year or month it is in relation to the other Phase Two films. But yes, it's the same time." So, while it may take place at the same time, just how connected will it be to the aforementioned films? "Certainly more than the others. We've already said that Thanos plays a part in it and is a character in it. That in and of itself should tell you it's connected to the other worlds." Talking of Thanos, many fans expected the Mad Titan to be the main villain in the sequel to The Avengers, but it was recently confirmed that it will be Ultron who fills that role. So, will he be the main foe in Guardians of the Galaxy? Not quite! "Ronan The Accuser is very much the main bad guy. And Thanos is lurking above it all. You will learn more about Thanos in Guardians, for sure. Certainly you'll get more than the one turn around and smirk. You'll get much more than that!"
Source: Empire Magazine via Comic Book Movie