Loki himself, actor Tom Hiddleston, says the upcoming "Thor: The Dark World" is as much sequel to "The Avengers" as it is to the first "Thor" movie.
Of his role in the film, Hiddleston tells MTV News:
"Loki has a very complicated relationship with Thor. He is an agent of chaos without equal in the world he inhabits.
He knows his true nature. He knows he doesn't belong in the family of Asgard, and he's locked away in the beginning of the film in the deepest, darkest recesses of the dungeon as public enemy number one.
Lo and behold, Asgard needs his help. That's going to be a very complicated allegiance. You'll have to see what happens in 'The Dark World' to find out where Loki finishes up."
Of the film's villains, he says the Dark Elves have "an ancient, ancient grudge" against Asgard and Odin. He also says that, if he were to come back in a future "The Avengers" film, he'd love to see Loki settle some "unfinished business" (ie. fight) with The Hulk.
Speaking of 'Avengers,' Hiddleston also sent out a tweet in support of the casting of James Spader as Ultron saying: "Go on, James Spader. Go get 'em @Avengers #AgeOfUltron".
There's also a new extended TV spot for "Thor: The Dark World" which you can see below: