Malekith, the ruler of Dark Elves of Svartalfheim, was involved in several Thor stories; however, he played no part in “The Infinity Gauntlet,” which will play a key role in future Marvel Studios films. His major storyline involved the search for an artifact called the Casket of Ancient Winters, which, if destroyed, could potentially turn a planet (Earth was the planet of choice in the comics) into a frozen wasteland. I believe the artifact was casually mentioned by the Frost Giants in the first film, so one could easily surmise that its power will be on full display in Thor: The Dark World.
Regardless of your opinions on G.I. Joe: The Rise of Cobra, you cannot argue that Eccleston did a fine job as the villainous Destro. He more than proved his ability to play evil, so he will likely excel as Malekith. We will find out when Thor: The Dark World hits theaters on November 3, 2013.