The official Legend of Zelda fan page on facebook has announced that Skyward Sword will contain more than 100 minutes of cinematic cut scenes in the game. Nintendo has also announced this game would contain 50-100 hours of gameplay as well. Along with these announcements, it was also said that the game would feature a secondary quest after completion of the game and a boss replay mode and hint movies as well.
The game having 100 minutes of cut scenes basically adds an animated movie to the game, and don’t forget these 100 minutes does not include gameplay time.
Source: Legend of Zelda Fan Page