The current voice actor for Ash Ketchum in the English dub, Sarah Natochenny, has posted her voice over resume on her website and the first title she lists is the upcoming 11th Pokémon Movie. According to her website the title for the new movie will be "Giratina and the Sky Warrior". There is currently no release date other than 2009 for the dub release.
The movie Giratina and the Sky's Bouquet: Shaymin (ギラティナと氷空の花束 シェイミ) as it is called in Japan, is the second Pokémon movie of the Diamond & Pearl movies trilogy, and the eleventh Pokémon movie overall. It premiered in Japan on July 19, 2008. The movie will be released on DVD in Japan on December 19th.