I saw a thing last week about this getting a 3-D Blu-ray release, but this is the first I've heard about it getting a theatrical screening.
My reaction: "huh?" and "why?" Okay, yes, there's some obvious season 9 promotion going on, but thing is, Dark Water and Death in Heaven are two episodes which just don't have very many visual effects in general, let alone anything that's really going to benefit from 3-D enhancements. That and they are dark episodes, meaning they aren't brightly lit. Dark Water is largely set in a dark mausoleum or balcony of the Nethersphere and Death in Heaven's action is set either at night or cloudy gray sky days. Watching this while wearing 3-D glasses is going to create what I call the sunglasses effect. But then, no one seems to mind this with all the dark 3-D movies, so what do I know?
Still, aside from the skydiving towards the TARDIS there isn't any impressive visuals in the episodes at all. In fact, they are very talky pieces with entire scenes, even the whole climax devoted to people standing around delivering dialogue. Not exactly a compelling reason to go to the theatre to see the episodes in 3-D or spend extra money on the special Blu-ray.