Japanese website AV Watch has official details on the Blu-Ray release of Ponyo in Japan. Studio Ghibli's latest feature film will be released on December 8, and will include standard and deluxe packages.
The standard-edition Ponyo will include English subtitles, but no English soundtrack. The Disney dub will not be included. No significant extras will be included, either, apart from what is available on the standard DVD. This BD will retail for 7,140 Yen ($77 USD).
The deluxe-edition Ponyo will include the extensive making-of documentary, and the Joe Hisaishi in Budokon live concert disc. The extras will not include English subtitles. This BD will retail for 19,110 Yen ($205 USD).
No official announcement has been made on Ponyo's DVD and Blu-Ray release in the United States. Both are expected to be released before the end of the year. Ghibli Blog will report on the latest developments.
Edit (2:50pm): I'd like to add one important point. Asian Blu-Ray is reporting that the Japanese Ponyo Blu-Ray will include multiple language soundtracks, including the English-language dub. I would expect this, given that Studio Ghibli includes the American soundtracks whenever possible. The Mononoke DVD even includes eight soundstracks on a seperate disc. If the John Lasseter Disney dub is not included on the Blu-Ray, I'll be shocked.