Pokémon Shuffle Version 1.1.12 is available for players of the game and the patch adds the Regirock Special Stage and 10 new Normal Levels. The Regirock stage will be available to play between May 11th, 2015 at 06:00 UTC and May 25th, 2015 at 06:00 UTC.
Details of this event have been added to our Pokémon Shuffle Special Event page.
Source:
http://www.pokemon.co.jp/ex/poketoru/news/post.php/39/ and
http://www.pokemonshuffle.com/en-us/connectivity#regirock-launch