Avalanche Studio CEO Christofer Sundberg has made clear in an interview with Swedisch Magazine Kong that they are working on a second game of Just Cause. Just Cause has only been released one month ago.
You will still play as Undercover-Agent Rico Rodriquez but you won't be playing in San Espirito anymore. The new location or any other information about the game haven't been given yet. Just Cause will be released on Xbox 360 and Playstation 3.