This time around, the information is being pulled from the Windows Phone 8.1 emulator. It seems that the emulator has a number of language pack files in it for Cortana. In total, there are 15 languages/regional language variations that could be supported by Cortana at launch. The language packs found in the emulator include: German, English (UK, US, and India), Spanish (Spain and Mexico), French, Italian, Japanese, Polish, Brazilian Portuguese, Russian, and Chinese (Cantonese, Hong Kong, and Taiwan).
It has been confirmed that at least the Polish language pack includes the same voice commands available in English, so it could well be that each language will have the full range of voice command options without limitations. However, there have also been reports that the language packs for non-English languages don't include the same files, which means Cortana could be English-only at launch.