This is the new character and his name is ?. The developers refer to him as "Dude". If you haven't checked recently there is a whole bunch of new stuff on the site. On the home page there is a video of the world map and on the dev blog there is new stuff about weapons and that's where this guy got revealed. Check it out here
. You can also see a new trailer at the bottom of the page here
Edit: Right after I made this they added a new video so I have new information!