Swedish development house Avalanche Studios have just posted a YouTube clip entitled 'Avalanche Studios in the Jungle', covering their Costa Rica trip to gather information and inspiration about complex environments for future games.
The video description notes: "In the spring of 2013, developers from Avalanche Studios traveled to Costa Rica to gather reference material for future games.
"... Just Cause 2 is used as an illustration throughout this video, but the reference material collected will prove useful in many of our upcoming open world games. In fact, some of the skies that we captured in Costa Rica will make it into Mad Max, which is currently in development at Avalanche Studios in Stockholm."
Although not explicitly stated, given the locales, it undeniably sounds like a little teaser for what's to come for a Just Cause sequel.