Nokia Lumia 1020 won't get new camera features from Lumia Denim update20
Some Lumia owners are reporting that their phone shows it running Lumia Denim even without receiving an updated firmware version number. That is because some models don't require the new firmware to support the new features coming to that specific model. For example, the Nokia Lumia 920 and the all-time favorite Windows Phone handset, the Nokia Lumia 520, are not receiving new firmware. So when either model hits Windows Phone 8.1.1, either via an official update or through Preview, the phone will "switch" to Lumia Denim.
On Wednesday, Microsoft is expected to unveil Windows 10 for Phones. We should find out then if older Lumia models will participate in the update.
source: Microsoft via WindowsCentral