A very language specific glitch.
A new glitch seems to be affecting Skyward Sword HD players who are playing the game in Dutch. After defeating the final boss they are greeted with a white screen and nothing happens.
The glitch seems to be tied to the language setting as some are noting that changing it to another language before the end battle avoids the glitch. Another user suggested skipping the first cutscene after the end battle will still let you experience the other parts of the ending, without changing the language.
Source: Nintendo Life