The original film, "G.I. Joe: The Rise of Cobra," cost considerably more to make ($175 million versus "Retaliation's" estimated $135 million) and made around $303 million internationally. If "G.I. Joe: Retaliation" continues at its current pace, it will end up with about $410 worldwide, which is, mathematically speaking, pretty dang good.
"G.I. Joe: Retaliation" was delayed nine months for re-shoots and a 3D conversion, and it's speculated that the third film will be shot in 3D to avoid the costly and timely conversion process. (Also, if your movie is in 3D, then it has a better chance of being one of the handful of American movies released in the lucrative Chinese market.)
Creative principles have yet to be locked down for the third film, but it's assumed many of the (surviving) cast members will be back for another high-powered go-round.