According to Holywood Reporter, Takahata's remark at Locarno Festival is not an official announcement of Studio Ghibli.

Source: Hollywood Reporter
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According to Asian Movie Pulse, anime director Takahata Isao announced Studio Ghibli's new film "Taketori Monogatari (The Tale of the Bamboo Cutter)". It will be premiered in 2010.

Suzuki Toshio mentioned the new movie last August in his Podcast program. Takahata will adopt the art style of Choju Giga, a Japanese classical picture scroll (so called the oldest manga).

Source: Asian Movie Pulse

Taketori Monogatari is a Japanese classical fairytale.
Tale of the Bamboo Cutter on English Wikipedia