I don't know if it's been finalized, but according to
The Disney Store there won't be lossless Japanese audio on the US release of Ponyo...
•Presentation: Widescreen 16x9, 1080p Hi Def
•Aspect Ratio: 1.85:1
•Sound: English 5.1 DTS-HD MA, Japanese Dolby 5.1, French Dolby 5.1
•Primary Language: English
•Subtitled: English, Japanese, Spanish, French
•Dubbed: Japanese, French
•Closed Captions: Yes
•Running time: 90 minutes
•For Region 1 use (US and Canada) only