There have been many confirmations from multiple carriers that Windows Phone 7.8 update will arrive at some point this month.
The last operator to announce that the rollout of the upgrade would start this month was O2 UK. However, none of the carriers confirmed an exact release date for Windows Phone 7.8, except Telstra.
The Australian carrier has just revealed on its official supports site that it might approve the Windows Phone 7.8 update on January 21.
Moreover, Telstra also mentions the upgrade will be available for Nokia Lumia 800 owners beginning January 31.
Other Windows Phone handsets confirmed to receive the update have been listed as well, but there are no exact release dates for the moment: Nokia Lumia 610, HTC Titan 4G, HTC 7 Mozart, HTC HD7 and Samsung Omnia W.