Almeno secondo quanto riportato dal sito Tech ARP:
Microsoft will be deploying Service Pack 1 in two "waves". Wave 0, which is the one released on February 4, will only include five languages - English, French, Spanish, German and Japanese. The second wave, Wave 1, is scheduled for release 1-2 weeks later, and will cover all 36 basic languages, including Chinese.
Fonte: Windows Vista Service Pack 1 Out Next Week!