Marvel's Thor: The Dark World is not just the first non-Iron Man sequel that will be released as part of Phase 2, it's also the studio's guinea pig for testing out a Fall season launch date. The film boasts Chris Hemsworth's third performance as the God of Thunder and was included as part of Marvel's 2013 Comic-Con panel lineup, despite Hemsworth being unable to attend the event in person. Unfortunately, The Dark World ended up gaining more attention for costar Tom Hiddleston's Hall H appearance in character/costume as Loki, more than the accompanying sizzle reel presented (complete with never-before-seen footage).
Meanwhile, the other remaining Phase 2 films - Captain America: The Winter Soldier, Guardians of the Galaxy and the newly-titled Avengers: Age of Ultron - hogged the spotlight, by making a stronger impression overall (according to members of the Screen Rant staff who were in attendance). The Thor sequel will get a second chance to get the Marvel fanbase stirred up soon enough, as the film's next trailer will be released online - and (simultaneously?) in theaters - next month (i.e. August 2013).
Youtube has announced a special week of programming from August 4-10th known as "Geek Week," which is a seven-day period that is dedicated to highlighting geek content. The event will include talent from popular Youtube channels, such as The Guild creator/cast member and Supernatural costar Felicia Day's Geek & Sundry (series like Tabletop and Fetch Quest), in addition to Stan "The Man" Lee's World of Heroes (programs includes Stan Lee's Super Model and UnCONventional).
Marvel will premiere the new Thor: The Dark World trailer on Wednesday, August 7th, in conjunction with Youtube's Geek Week festivities. It's not yet confirmed, but the general expectation is that part of the footage shown at the Marvel's 2013 Comic-Con will be included in the new theatrical preview (though perhaps not the semi-spoilery clips that were contained in that sizzle reel).
The Dark World Comic-Con footage, like the material shown in the first trailer, is described as having a Game of Thrones-esque vibe, thanks to the overall grittier filmmaking style and tangible production design favored by director Alan Taylor (a former co-showrunner on HBO's popular Medieval fantasy series).
Returning cast members Tom Hiddleston (Loki), Natalie Portman (Jane Foster) and Anthony Hopkins (Odin) will each have an important role to play in the sequel. In addition, some of the characters who were sidelined or under-used in the first movie - like the lady warrior Sif (Jaimie Alexander) and the powerful Asgardian gatekeeper Heimdall (Idris Elba) - may get a more significant amount of screen time, based on past interviews and the footage shown to date.
Thor: The Dark World opens in theaters on November 8th, 2013, followed by Captain America: The Winter Soldier on April 4th, 2014, Guardians of the Galaxy on August 1st, 2014, Avengers: Age of Ultron on May 1st, 2015, Ant-Man on November 6th, 2015, and unannounced films for May 6th, 2016, July 8th, 2016 and May 5th, 2017.
Source: Marvel Studios