Some thoughts on Thor 2...
Apparently Tom Hiddleston would like it if Loki somehow found redemption. Considering the events of the Avengers and Thor before that, the lives which Loki has destroyed, ruined, or caused anguish to have makes it difficult for him to go about that route without something truly significant to make up for it. Assuming that Loki faces punishment at the hands of Asgard and not his benefactor (you-know-who), I can see Loki fighting on the side of good if it benefits himself. If we do happen to get a threat on the scale of Surtur, it would be awesome to see Thor, Loki, and Odin fight together to stop him, similar to Walt Simonson's epic run.
I'd definitely like to see more of the Nine Realms explored in addition to Asgard and Midgard. This might be difficult as Thor is somewhat anchored to Earth due to his relationship with Jane Foster and the Avengers, though. I don't think Enchantress and Executioner would be proper foils for Thor, at least not for the main threats; I'm not opposed to them being in the movie, but the threat of Loki usurping the throne and ravaging Jotunheim is more significant than say, Amora simply trying to seduce Thor and win over his heart and Skurge being her muscle. Surtur or Hela would be great choices as they can challenge Thor in the immediate sense and also on a much larger scale.