Why not release it on its original date? Then when people stop going, just add in the 3-D. People will pay a few extra bucks for that right? I mean it works with games. Just like this:
Then, a few months after that, say when the 9 months are up, just sell this to moviegoers for a few bucks.
You know, I could be on to something here. It's not hard to see where this culminates. When released on video, bundle them all together for the G.I. Joe: Retaliation MotY (movie of the year) Edition!
To be clear, I'm okay with the idea of DLC, just some of the execution could use some work (read: less greed). I don't think this would fly in any other form of entertainment, so hopefully this doesn't ever happen to movies or TV shows. But I know my wife would buy a Tom Baker add-on costume for the latest Doctor Who so she doesn't have to see Matt Smith. Now I might be on to something...