It is coming on April 15, 2011.
Here's the first concept art for this, depicting the re-creation of the grand ballroom where Cinderella and Prince Charming met, danced, and fell in love:

Tokyo Disneyland Announces Cinderella's Fairy Tale Hall
It sounds like Cinderella is opening up a museum with precious or famous art! And she's such a kind princess, as we know her to be, to open up her castle to everyone, even when she's gone, so they can share in her good fortune, beauty, and magic.(October 15, 2010) Tokyo Disneyland® Park announced its decision to open a new attraction titled Cinderella’s Fairy Tale Hall. This will be a walkthrough-type attraction located inside Cinderella Castle. Guests can wander through gorgeous rooms that bring to life the world of the Disney classic film Cinderella and view paintings, diorama, and other artworks that follow the story of the beloved princess. This new attraction, where guests of all ages can immerse themselves in the world of Cinderella’s fairy tale fantasy, is scheduled to open on April 15, 2011.
Cinderella’s Fairy Tale Hall is located in the castle where Cinderella lives with Prince Charming. Cinderella, wanting to share her magical princess story, decided to open up the castle even during her absence and exhibit various artworks that show scenes from her story.
At the lobby and corridor, guests will find eight murals showing how Cinderella changed from beloved daughter, to servant girl, and then to Princess. They will also see a diorama of Cinderella magically transformed into wearing a beautiful ball gown, and other artworks made from various materials such as paper, wood and glass. In the Grand Hall guests will find a magnificent chandelier, the renowned glass slipper, a throne, and special paintings that reveal a magical message when photographed using a flash.
Attraction Outline
•Location: Inside Cinderella Castle in Fantasyland
•Attraction type: Walkthrough
•Total capital invested: Approximately 2 billion yen
At first I was worried that because it was called Cinderella's Fairy Tale Hall, it would be about more than just Cinderella's fairy tale, like her castle would be home to many different Disney fairy tale films. But it was confirmed it would all be all about the girl with the pumpkin coach, mice, and glass slipper!
I was also worried that the planned attraction for Walt Disney World's Fantasyland expansion of Cinderella's chateau and show was just going to be copied and used as this attraction, but this will be a completely seperate, different attraction. There won't be a live face character Cinderella getting transformed like Disney World's attraction was supposed to have, but a diorama of the scene for this Hall!
I couldn't be more excited. It sounds better than I ever dreamed, and like a dream come true! I cannot wait, it is the must of my places to ever go!
