Chris Hemsworth returns as Thor in Thor: The Dark World.
From IMDB:

Thor battles an ancient race of Dark Elves led by the vengeful Malekith who threatens to plunge the universe back into darkness after the events of The Avengers.

Natalie Portman also returns as Jane Foster.
Thor: The Dark World is due out in theaters on November 8, 2013.

Though, I think Thor was the weakest of the first phase of movies, I still thoroughly enjoyed it. I am very much looking forward to the sequel’s release and anticipate that only increasing once Iron Man 3 is released.