People make a mistake assuming the EOS wil canibalize the 920.They are not in the same class and they never were.
The 920 is the mainstream flagship device that goes against the iphone,sgs3 and onex. It has a one year life cycle just like any other product.
The EOS/808 pureview is a niche device, a uber camera smartphone. It has it's own year life cycle(aprox) and it will be more expensive then the 920.
And don't fall in the trap of android devices. What i mean is compare it with the devices that are released every 5-6 months from lg and sony for example. The galaxy s3 and the htc one x both had the standard one year life cycle. This is because they are good devices, that sell, and you need that cycle to make sure you make back your money from development and some profit. Now the reason why lg and sony released flagships every 5 months is because those devices were always poor,always behind the market or with quality issues. That is a problem for them because by releasing at such a high frequency rate flagships they don't have time to recoup their costs and make a profit so they are always making loss. Sony had in a one year time frame the ion,xperia s, then a refresh with xperia t,and now xperia z. 3 flagships in exactly one year time. That's not a good bussiness. And lg did the same and it's doing it now with the optimus g and all the variations from the last months.
So nokia is doing the right and sensible thing and manage their protofolio accordingly. In fact this is the first year since they went with microsoft that they can really show what they could do with wp and the first year they have a full lineup of devices just like they had in the good old days before the problems started. And they need this full portofolio to go against samsung who uses the same strategy nokia had when it was profitable, and that is have a device in every price point for every niche possible in all the regions of the world. So now that they have this mainstream protofolio, during the year they will have the next asha refresh(which they need to battle the ever cheaper androids and new the oses like firefox) and the niche devices like the EOS. In fact they probably need an even greater portofolio with either another more liter pureview or a device like the galaxy note(it was rumoured last year that nokia is toying and has plans for a note competitor).
Conclusion : NO, EOS is not hurting the 920, YES, nokia needs the EOS and other niche devices( in the good days they had a camera centric device, a bussiness series, a fashion series, developer devices) to gain back profitabillity and to increase sales