I got this from Serebii.
"The release details for the upcoming movie; Giratina & The Sky Warrior, appear to have been released via an online retailer listing. This lists the release date as March 31st 2009. This movie ties in with the Platinum games in featuring Giratina's Origin Forme, Shaymin and an alternate dimension. This release date is tentative and may change at any time."
I also have read some rumors about the Pokemon Movie 12 (Japanese title is "Towards the Overcome's Time Space!"), and the rumors are that it involves Arceus, the "Poke God". A small trailer revealed a special Pichu known as the Notched-Ear Pichu that is supposedly involved, as well as Dialga, Palkia, and Giratina.
In accordance with the 11th movie release in the US, the Shaymin Event was confirmed by Toys R Us, and it will be going on from February 8th - February 14th. Also, due to a leak from Ultimatedra who works at Toys R Us, the Regigigas event will also be held at Toys R Us following the Shaymin Event. It will be going on from March 8th - March 21st.