Thor 2 Movie - Thor Sequel

The first Thor movie hasn't been released yet, but Marvel is already planning a movie sequel to Thor. Most actors of the first film have signed up for multiple Thor movies. Actress Natalie Portman recently confirmed the thing to MTV:

"I'm supposed to be in the next 'Thor' if they make more, but I don't know about that. I think all of us are signed up for the rest of the 'Thor' series, but we could have one line in the next one, or nothing."

Actress Natalie Portman

The's no doubt indeed that Chris Hemsworth will reprise his role as Thor. And I guess Director Kenneth Branagh would be quite glad to be back to helm Thor 2. The director has actuality already joked about getting a small role in the sequel to Thor (I guess he's thinking about emulating Jon Favreau who showed up in Iron Man 2).

The first Thor movie will revolve around Thor trying to get back to Asgard (he will face both the Destroyer and Loki then). And Thor will likely have to face Hulk and maybe the Skrulls in the upcoming Avengers movie.

So who could be the next villain in the movie Thor 2? Any suggestion?
:)