As per the shared information, Microsoft is expected to release the Windows Phone 8 GDR3 soon but not all features will be supported in low end devices such as Lumia 520. Certain features will be limited only to the hardware with 1 GB or higher RAM. Windows Phone 8 GDR3 might be packaged as Bittersweet Shimmer on Nokia's Lumia devices.
Cortana, personal digital assistant for Windows Phone devices, is expected to arrive with the Windows Phone 8.1 Blue update. Windows Phone 8.1 Blue update will initially be released for the US region. In the rest of the world, Windows Phone 8.1 Blue might be released in the latter part 2014. Not only that, Nokia Pro Cam app and Glance screen feature will not even be available to all Windows Phone devices.
Nokia is expected to launch a new large screen Lumia 1520 smartphone with full 1080p HD display and Windows Phone 8 on 22 October.