Diego Luna joins Neill Blomkamp's Elysium

We still don't really no jack about Neill Blomkamp's follow-up to District 9, the political sci-fi film titled Elysium. Supposedly the film will have some of the same tones and themes as his debut feature, but pretty much that's it. Well, that and he's gathered a crazy line-up to star in it. Jodie Foster is apparently some sort of leader of an alien planet; Matt Damon is involved somehow, along with William Fichtner, Alice Braga, Wagner Moura, and let's not forget Sharlto Copley. Makes me think Blomkamp struck some sort of "awesome casting" deal with the devil.

Variety reports a new addition, and keeping with the rest of the crew, this one's another heavy hitter. Diego Luna(Y tu Mama Tambien) will play Julio, the best friend to Matt Damon's character. Luna was most recently featured in Milk, opposite Sean Penn. He'll be seen next in Contraband, starring alongside Kate Beckinsale and Mark Wahlberg, and is a part of Will Ferrell's Spanish language comedy, Case de mi Padre. 

So what's the deal with this film, anyway? Why's it being kept so secret? Variety now describes the plot as humans doing battle on Earth. That's way too simplistic to be all there is to it. District 9 tackled themes of prejudice and hatred, drawing parallels with the South African apartheid. I'm dying to know what angle he'll come from this time.