Production on Thor: The Dark World is expected to begin later this month in London, and while the details of the plot have yet to be confirmed, a casting call for background actors has indicated where the sequel might going.
What we know for sure is that many of the key characters from the first film will be returning, including Thor (Chris Hemsworth), Jane Foster (Natalie Portman), Odin (Anthony Hopkins), and Loki (Tom Hiddleston), along with secondary characters like Heimdall (Idris Elba), the Warriors Three, and Thor's mother, Frigga, played by actress Rene Russo (Get Shorty, The Thomas Crown Affair).
[WARNING! POTENTIAL 'THOR 2' SPOILERS BELOW!]
Rene Russo recently spoke with Vulture about her role as Frigga in the first film and what her responsibilities might be in the sequel, saying:
"You know they cut me [down] in the first film. [Director] Kenneth Branagh sent me a nice note, because he understood, he's an actor. You move on, what are you going to do? But I think they're going to need a good mom in the next film. Loki needs his mom. What the hell?"
Frigga spent the majority of Thor by Odin's side as he falls into the Odinsleep, helping to protect him while also trying to reassure Loki of his importance to their family (after Loki discovers his relationship with the Frost Giants).
Russo also discussed how Frigga might perceive Loki following his actions in The Avengers, and teased a possible plot device concerning her character and Thor:
"I have a lot of compassion for [Loki]. But we might have to have a conversation about what he just did. And I might have to have a chat with Thor. But I am so confused - is Thor my son or not? People have been telling me recently, 'No, you're not his mother.' It's all so confusing. I got to tell ya, it would be a little embarrassing if I don't know. I need to read more about her."
Actually, Frigga is Thor's stepmother, not his biological one. It's still unclear whether this will be explored in Thor 2, though it's worth pointing out that, given the speculation over the film's story (along with it possibly having to spend time setting up other "Phase II" films for Marvel), there simply might not be enough time to delve too deeply into this issue.
What seems more likely is that Frigga will deal primarily with Loki, as Russo hinted at. Thor took Loki back to Asgard at the end of The Avengers to face Asgardian justice, and it certainly seems plausible that Frigga could influence whatever ruling is made.
If nothing else, she could be seen trying to console Loki and repair the damage to his pride and overall frame of mind after the events of Thor. The importance of family was a major theme in the first film, so it's not out of the question for it to remain in the spotlight in the follow-up, particularly if Asgard is featured more prominently.
Thor: The Dark World is slated for release on November 8th, 2013.