Nintendo will release a free Pokemon game for 3DS, in Japan at least, revolving around the events of the upcoming movie.
This game is based upon the movie Diancie and the Cocoon of Destruction--the seventeenth Pokemon movie, for those keeping count--which will see a theatrical release in Japan this July. Known as The Band of Thieves & 1000 Pokemon, the title refers to the villains from the movie and will be a StreetPass-focused affair where you collect Pokemon from passing other players and then challenge opponents. The team with the strongest side wins.
Pokemon supersite Serebii.net posted the information from the latest issue of Japan's CoroCoro magazine, which regularly posts new information about Nintendo's long-running series. The game is said to be coming to the Japanese eShop on June 5, and will be available for a limited time.
It is also said that the The Band of Thieves & 1000 Pokemon will offer up a special Pikachu, which will be music to the ears of any devoted Pokemon trainer.
While Nintendo has not confirmed a release of The Band of Thieves & 1000 Pokemon outside of Japan, the company has recently announced a few Pokemon titles for worldwide release: drawing title Pokemon Art Academy and Pokemon remakes Omega Ruby and Alpha Sapphire.