As mentioned earlier, it will boast of many features from the Windows Phone GDR3 update, including rotation lock, custom ringtones, Nokia Camera, Storyteller, Bluetooth 4.0 LE support, and richer notifications on the lockscreen itself. The update should also have 3051.40000.134x.00xx as the update version, while for the Nokia Lumia 1520, it would receive a bump to version 1028.3534.1347.2001, where that will come with general performance and usability improvements. These updates will cater only for US AT&T devices at this point in time without any confirmation on whether it will arrive on international handsets soon. For those of you who want to perform a manual update, do go into Settings > Phone Update > Check for Updates, and make sure that you are connected to a Wi-Fi network beforehand.