I'm pretty sure the speech is prerecorded because I think the family likes to pass the Christmas season at their chalet in Switzerland. If you are one of those people who just has to have a source for everything you can check old issues of the Spanish language magazine Vanidades.
In honor of the upcoming speech of The Duke I thought it would be a good time to reflect on last year's message. The text of his previous speech may be read in English, French, and Luxembourgish. You may also view his speech in Luxembourgish. I have attached the speech. Remember this is the message from last year. When the new message comes online I'll make a new post for it.
Christmas Eve broadcast 2008