Don't forget theaters paid through the nose to upgrade their systems to 3D. You can bet it's going to stay around long enough for them to make some of that money back through inflated ticket prices.
Also, doesn't this really just mean that 3D has been accepted and is now a standard feature on new TVs, like color? You have no choice but to get it (and pay for) most of the time.
3D is making money hand over fist worldwide. It is doing better outside of North America actually, where 3D hasn't done as well at theaters.
Life of Pi was pretty awesome in 3D. In the hands of the right filmmakers, it enhances the medium. Of course, it can also really suck too. The price differences here between the two are small, but significant.
edit:
That's a good point about it being accepted. I don't think so though. From what I read 3D home stuff has sold poorly. I don't know if they've given up on it, or are just going to push what they already have for years to come.