Shiny Silvally event has been announced!
Add a Shiny Silvally to Your Ranks
Don’t miss out on your chance to collect a uniquely colored version of the Synthetic Pokémon Silvally.
Power up your Pokémon party with a bit of Legendary Pokémon flair by visiting a participating GameStop and EB Games where you can pick up a code card that allows Trainers to receive a Shiny Silvally in their copy of Pokémon Sun or Pokémon Moon. Shiny Silvally radiates in battle with its RKS System Ability, and you can give it a memory disc to hold to change its type, then unleash its signature Multi-Attack! Act fast! These code cards will only be available from October 23 to November 13, 2017 while supplies last, and the codes must be entered by February 13, 2018. Don't miss out on Shiny Silvally!
https://www.pokemon.com/us/pokemon-news ... our-ranks/
As well as US/Canada dates/locations, UK distro details were announced - November 3rd through 16th, at GAME (and, likely, the usual code stores everywhere else)