The new issue of EW not only features three new photos from Marvel's ambitious and cheeky space opera "Guardians of the Galaxy," it also boasts quotes from director James Gunn about how this movie fits into future Marvel movies.
Though labelled "only stand-alone adventure" of Marvel's Phase Two, the events here are "definitely connected to The Avengers 3". A big part of that is the villain Thanos who will be portrayed through motion-capture.
In relation to the other villains in the movie, Thanos is "the head of the snake." He's also got a big hand in the back stories of Gamora (Zoe Saldana) and Nebula (Karen Gillan): "Thanos slaughtered [Gamora's] family and Nebula's, then raised them together as siblings. They were bio engineered to become living weapons, so he's really good at killing people."
Source: Entertainment Weekly