This from Blackfilm.com:
"Through a reliable source, Blackfilm.com has learned exclusively that an offer has been made to rising star 'District 9' Star Sharlto Copley for the role."
Off course at this point this is only a rumor. There has been no confirmation that Copley has accepted yet. Among the other actors mentioned for the role Jim Carrey, Steve Buscemi, Timothy Olyphant, Woody Harrelson, Sam Rockwell, Chris Pine and Robert Downey Jr. You can throw all these guys out the window except for maybe Sam Rockwell.
After the 4 star performance that Copley put into Distric 9 I'm surprised he hasn't been offered more roles. Just in case you don't know who Copley is I have included a picture below for your enjoyment.