Lumia Denim update coming soon according to message from Microsoft Lumia23
The update combines some of the goodies from Windows Phone 8.1 update 1, and the Lumia Denim firmware update. Some of the new features include changes to the Glance screen so that Bing Weather can be viewed. You will also be able to have some of the Bing Health and Fitness data appear as well. The update also turns on Cortana (NOT the way you might have been thinking) when you say "Hey Cortana". Other changes include a quicker time between shots with the Lumia Camera app, and certain models will offer improved imaging with the rear-facing camera.
The update is expected to take two months to complete. If it does start rolling out this month, it might be the end of January before the Lumia Denim update has been sent out to all Windows Phone handsets that support it. Most of you will find it well worth waiting for.
source: @Lumia, NPU via WMPoweruser