Update:
While Juha clarified ( read below ) that Lumia 1020 won’t get the camera speed improvements with Lumia Denim due to oversampling and huge sensor size, we have kind of hoped that Lumia 920 and Lumia 925 without big sensor or oversampling may get some speed improvements. The answer is “no” again, unfortunately.
@Nokiapoweruser Unfortunately it doesn’t.
— Juha Alakarhu (@jalakarhu) September 16, 2014
Though, we tried to find out and can share that the Lumia 830‘s Moment capture ( Full HD, 2-megapixel per frame quality) may makes its way to older devices later. Don’t ask, when?
Read all about Lumia Denim and Windows Phone 8.1 update 1 at our dedicated page.