Hidden Fates Elite Trainer box is now back up on Pokemoncenter.com (currently unavailable). It was taken off a couple weeks ago. One can assume that they are preparing to release it again.
Pokémon TCG Hidden Fates Elite Trainer Box - US
Homepage | Pokémon TCG: Hidden Fates
POKÉMON - ELITE TRAINER BOX (ENGLISH) - HIDDEN FATES