Profiles published by Apple suggest March 9th launch of iOS 5.1
Additionally, the update could help Siri understand some new languages. Chinese Tech site DoNews says that Mandarin Chinese will be added to Siri's repertoire, possibly with the iOS 5.1 update at the same time that the voice-activated personal assistant becomes "fluent" with Japanese and Russian. Apple has said that Siri would be undergoing some intensive Berlitz training in 2012.
According to YourDailyMac, eleven new profiles for were published by Apple for those carriers selling Apple's touchscreen smartphone in Japan, France, Greece, Finland and Sweden. The profiles guarantee network connectivity after the update and not only mention iOS 5.1, but also displays a launch date for the update of March 9th. On that day, we could see a release of the next iOS version for the Apple iPhone, iPad and iPod touch.
source: YourDailyMac, DoNews (translated), TUAW via BGR