The 1020, imo, is made for photographers in mind, such as those who are hobbyist and pros who just want a point and shoot that works. Not necessarily for the general consumer who just take photos every once in a while. To me the 920 allows low light photos, which is when most consumer photos happen because social things usually happen in the evening. Yes we would benefit from the oversampling, but consumers are usually taking photos for Facebook, not so much for post processing and printing, which is what the 1020 seems to be geared for.
For most people who are excited for this, I'd say most of them just want to own the flagship device, the best device that Nokia is offering, i.e. supporters of Nokia. The rest are actually enthusiasts who in their daily lives benefit from the camera tech offered vs just being able to show off to buddies.
So to answer the question, I think 920 users shouldn't upgrade to the 1020, unless they absolutely need that camera tech that can make changes in their lives (photography is a serious hobby/lifestyle). If that isnt you, just wait for the Amber update which should bring all the algorithms that the 925 and 1020 are using.