Storylines are already being drafted for Thor 2, and two early contenders for the main villains this time out are The Enchantress and The Executioner.
Hailing from Asgard, Amora is a powerful sorceress who calls herself The Enchantress, and she will attempt to destroy Thor's (Chris Hemsworth) love interest Jane Foster (Natalie Portman), so that she can have him all to herself. In the mythology of the original Marvel Comics, Loki (Tom Hiddleston) helps Amora accomplish her goal.
The Executioner is The Enchantress' right hand stooge, who is so in love with Amora that he will do whatever she asks, which may include killing Jane Foster.
These story ideas are at the very early stages of concepton, and Marvel doesn't suspect that it will have a script done until the end of this year. It is possible that Thor 2 will find itself in front of cameras as early as March of 2012.