Now that I’m back from Japan (I was at the World Championship) and the Power of the Duelist Sneak Preview surprise is out, it's time to implement a slight change to Yu-Gi-Oh! tournament policy that is effective immediately:
"Yu-Gi-Oh! TCG promotional cards become legal for all tournaments upon their formal release. Promotional cards that have not been formally released are not legal for tournament play."
Note the use of “formal” and “formally”. That would exclude any special cards which may have been pre-released for promotional purposes.
Senior Game Designer, UDE
Yu-Gi-Oh! TCG R&D Lead
Upper Deck Entertainment.