This trailer was initially released in Japan a couple of months back and served as an anime-style introduction to the game. Nintendo have recently released an English dubbed version of it and serves to introduce the game a bit differently from how they have in the past.
Pokemon Black/White 2 is due for release on the Nintendo DS in October 2012, on the 7th for North America and around the 11th-12th for PAL regions. This is the first time since Pokemon Gold/Silver/Crystal that they will be making use of the same region as a previous game (G/S/C featured both Johto and Kanto), however the scenario is completely new and the region/characters have changed in the years since the events of Black/White.