From Wikipedia "Although they do not currently own the Just Cause intellectual property, representatives of Avalanche Studios have expressed interest in creating a sequel and distributor Square Enix have reserved various domains for Just Cause 3 and Just Cause 4. There are also rumors of a possible movie, called "Just Cause: Scorpion Rising. "
maybe it's too early because just cause 2 came out after 4 years the original, so u can expect the third will come out in 2014!!!