G.I. Joe 3 is happening, and according to the poster out of the 2014 Licensing Expo the movie is coming soon.
Last we heard about G.I. Joe 3 is that Jon Chu will be back, but Chu will do the new Jem and the Holograms movie first.
Update: Now it's said Jon Chu will not be back.
It's also been said that Channing Tatum could return (somehow).
Here is the G.I. Joe 3 poster (via Coming Soon):