I am not a fan of game leaks and people letting out big game details that relate to how the games story goes or key features or as the case was with Pokemon X and Y last year all the mega evolutions and new Pokemon. Leaks are not a good thing and it is bad for the games themselves and I don't understand why you would want to ruin your potential experience with the key details of games. This is exactly what has happened with the Witcher 3: Wild Hunt and I have no plan to follow up on these leaked details. However I can tell you the leak relates to story, missions, enemies and ending details.
CD Projekt Red has acknowledged the situation, and has advised fans to avoid checking out the information.
According to marketing boss Michal Platkow-Gilewski:
“It has come to our attention that some of the production files for The Witcher 3: Wild Hunt have emerged on the internet. A portion of the files contains information about the story of the game so we strongly advise against accessing them, as this may heavily impact and spoil your future gaming experience. We also like to reassure everyone that the disclosure of said documents does not affect the development cycle in any way.”
So just to not ruin the game no matter how tempted you are don't go looking for the leaked details don't ruin your experience.