Update: The source page: http://www.nokia.com.vn/belle/sw has been removed by Nokia. After this page removal its still not clear when Nokia would roll out the Belle update. Though they had claimed February 2012 as the official release month for Nokia Belle on Nokia Conversations (The official Nokia Blog.)
Here comes an exciting news for all of you, according to Nokia Vietnam, Official Nokia Belle firmware upgrade would start rolling out from the second week of February 2012. They have also mentioned the roll out date: 08 February 2012. Further more, you can only upgrade to Nokia Belle using Nokia Suite or Nokia Software updater, Nokia Belle update won’t be available via Phone Software Update App (Over the Air – OTA) as its a major and huge update.
Ready for you to download from on 08-02-2012. The phone can be upgraded to Nokia Belle: Nokia N8, C7, E7, X7, E6, E7, C6-01 and 500
Those running on leaked versions of Belle would be able to upgrade to the Official Belle using Phoenix flashing.