Just like the 3DS demos, Wii U demos also have a limited amount of times that you're allowed to play them. As you can see, the FIFA 13 demo allows for 10 trials. We're not sure if the numbers will vary like they do with 3DS eShop demos.
PSA: This might be a good time to remind everyone that you can filter stories here on the site, especially if you are hoping to avoid spoilers of a Hyrulian nature. This is available only to registered members.
Edit Profile > Custom Filters > Games Type "breath" or other keyword to find a game, and make sure it says "Exclude".
Bam. Media blackout on that until you tell us otherwise.