What happened to Odin at the end of Thor 2?

At the end of "Thor: The Dark World," Odin is seen mourning the loss of his son, Thor, who has just returned to Asgard after defeating the Dark Elves. However, unbeknownst to Odin, he is actually speaking with Loki, who has taken on the guise of Odin while ruling Asgard in his place. This twist sets the stage for further developments in the Marvel Cinematic Universe, particularly in Loki's character arc.