According to Cinema Today, Shinkai Makoto's new anime movie "Hoshi o Ou Kodomo (Children who Chase Lost Voices from Deep Below)" was announced to be premiered in 2011. A trailer will be streamed on Yahoo Japan on November 9th.

Hoshi o Ou Kodomo official website
Team Shinkai official blog

Staff
Director & Scenario: Shinkai Makoto
Character Design & Animation Director: Nishimura Takayo
Art Director: Tanji Takumi ("5 Centimeters per Second", "The Place Promised in Our Early Days")
Music: Tenmon

Synopsis:
Asuna lost her father and lives a lonely life listening to mysterious music coming from her father's crystal radio. One day she sets out for a journey to see a boy again. Through the adventure, she experiences a parting and finds the cruelty and the beauty of the world.

Source: Cinema Today

Update
To be premiered next May.
Trailer: http://meta.yahoo-streaming.jp/webevents/yahoo/movies/hoshi-o-kodomo/trailer01_1m.asx (ASX via Yahoo Japan)
Copy on Youtube
Official website fully opened

Updated on Dec 22
Cast
Asuna; Kanemoto Hisako
Shun/Shin: Irino Miyu
Morisaki: Inoue Kazuhiko
Shimamoto Sumi
Hidaka Rina
Takeuchi Junko
Orikasa Fumiko

Source: Official blog