Primary speculation actually is South Asian map. They said it was something entirely new and fresh, so anything like Chernarus is out of the question, and desert was already done with Takistan. Arma 1's Sahrani has jungle elements, but it's also very mountainous, so a South Asian jungle wouldn't be out of the question, probably similar to Far Cry 3.
There was a picture I think on reddit some time ago found in promotional material of a third-party modeling company contracted by BIS, it had a bamboo hut and stuff. Although, it may not necessarily be related to the new map.
EDIT:
reddit threadEDIT 2:
more evidence in campaign cutscene