According to Serebii.net, the official Pokemon site has open a subsite that announces the aring of the 12th Pokemon Movie - Arceus and the Jewel of Life - on Cartoon Network November 20, which is a Friday. I assume that the time will be at 8:00 PM EST. The movie is the third installment of the Diamond & Pearl trilogy that involves Dialga, Palkia, and Giratina.
The site has also revealed that the movie will become available on DVD in the Spring of 2010. VIZ had not confirmed this at this time, but I assume that they will add it to their March solicitation schedule, or on their April schedule at the latest. It might also coincide with the North American release of the Heart Gold and Sould Silver DS games, though Nintendo has yet to reveal the actual street dates for those games.
You can view the movie's subsite and trailer here