After announcing Windows Phone 7.8 back in June, Microsoft has remained tight lipped on the exact availability of the update for existing users. The software maker has promised early 2013, but it appears that the update will be available to some devices at the end of the month. WPCentral reports that Nokia Lumia 900 devices on AT&T will receive Windows Phone 7.8 on January 30th.

The update will add the ability to resize Live Tiles into small, medium, and large options, and add some extra theme color options that are identical to the ones found in Windows Phone 8. Microsoft is largely appeasing existing Windows Phone 7.5 users by matching the visual style of Windows Phone 8 in its 7.8, but the majority of features will not be back ported. A fresh option to display the Bing homepage image on the lock screen is also included, but third-party developers will not be able to use this feature with their own apps.

The Windows Phone 7.8 update will be available to download through the Zune desktop software, and is expected to be around 100MB. A recent SDK release for 7.8 means the update will likely hit other devices soon too. We asked Microsoft for a comment on the Windows Phone 7.8 timing and a spokesperson says the company is working closely with "hardware and carrier partners to get it tested, approved, and rolled out to as many devices as possible in early 2013."