People don't realize the 1020 was a completely different device from the 808. They were moving it from Symbian to Windows Phone which is a huge overhaul. With a few leaked codenames coming out in June & July I wouldn't be surprised that one of them is the 1020 successor since the 1020 was released around that time last year. It would not make sense for a successor to be released in 2015.
EDIT: So the 808 WAS released a year before the 1020 in the US so why we wouldn't see a new version this year would be ridiculous.
Nokia 808 PureView - Wikipedia, the free encyclopedia
The core technology/concept is exactly the same. Optics design, pixel oversampling, pixel count, rich recording, etc. were all introduced on the 808 and ported to the 1020 with some relatively minor changes. The big addition was the OIS system..
Its much easier to PORT existing technology to a new platform than it is to introduce a completely different technology to the table.
If the jump from the 808 to the 1020 was as big as it was from the N8 to the 808 I would agree with you, but its no where near as big...
Nokia could either update the 1020 with newer hardware, or we are going to have to wait for a brand new design. The Microsoft transition isn't helping with all of that I am sure.
Nokia haven't done a minor model upgrade in a while, kind of like what apple does with the number -> letter > number thing
The 808 and the N8 were two separate projects with two separate timelines, so the fact that they came two years apart doesn't tell us much in terms of schedule. We know that the original PureView project took around 5 years from idea to market..