This from Chud.com:
"Even though he wrote District 9 with no sequel in mind, Blomkamp admits that he has “an inclination of an idea” for one and would definitely be interested in directing the sequel...
...which would again be set in South Africa and star Sharlto Copley as Wikus van der Merwe again. “Does Wikus become human again?” is one of the plot issues which Blomkamp feels can be explored in a possible sequel."
That would be cool as we would see Christopher come back to Earth with his alien friends and kick hell out of all the puny humans experimenting on and selling cat food to the aliens. Old people might not mind but seriously Cat Food!!!
When Neil Blomkamp was asked whether Christopher would return to Earth in three years to help Wikus. Bloomkamp states “I do have ideas rattling around in my head, and weirdly enough they're not to do with what you just said,” Blomkamp said. “They're different. But, who knows?”
That's not to say Neil Blomkamp wouldn't turn back the clock, so to speak. Apparently Blomkamp finds van der Merwe’s character to be “hilarious". District 9 star Sharlto Copley played van der Merwe and has also said he would love to play a younger version of the character.
Blomkamp also acknowledged the Peter Jackson would be involved in any future Prawn battles.
Still though I think the money shot is in the future. Let's see what kind of Hell on Earth Christopher would reign down in 3 years. That would be cool.