The 3D novelty is wearing off. Now, people think twice about going to 3D or paying the extra $$ to take the kids to a 3D movie.
Some movies are definitely 3D winners. Avatar, Transformers, etc. do a very good job of it.
A lot of films are just 3D rip offs. Just having a computer mess with the film to make it look like 3D.
I predict there will be 3D films for quite a while, but 3D conversion of 2D films will drop off. Once people stop paying to see a film conversion, it will no longer be worth the price. All the screens and projectors are in place, 3D will stay around, but I wonder if they will eventually have to stop surcharging for it?