Officially speaking, the delay in releasing GI Joe: Retaliation was for the completion of a 3D conversion and the shooting of a couple new scenes particularly designed for stereo viewing.
There are also pretty credible stories about plot rewiring and the injection of more Channing Tatum, to the point that More Tatum became a bit of a nascent internet meme for five minutes.
Here's a trailer for the new version of Retaliation. It's not in 3D, and we hadn't seen every bit of footage shot before the reworking, therefore it's impossible to tell if any of this actually comes from the new shoot or if it's all old.
GI: Joe Retaliation has been directed by Jon M. Chu who has previously played a pretty strong hand in dance pictures. If he can bring his skills with choreography to bear here, we might be in for a fun night out at the movies. The film reaches US cinemas at the end of March.