The device in the picture leaked above carries high-end design with Lumia like colored personality. The earlier leaked preview showed that it will sport 5 MP camera and a new UI with even more swipes and gestures !! Having a look at the above image shows that it will have Lumia like lock screen as well. The point we were trying to make here is that perhaps above image will just be placed below Lumia 5XX not only in price hierarchy but also in sales positioning. So, as we know current lowest Lumia numbering is 510 (505 in selected markets though) !!
Now if you remember a leaked Asha 509 device from RDA leaks reported by us. From those leaks Lumia 920 and Lumia 510 came true, so we can still think of other devices coming true at certain point in time.
This may make sense as well, because going ahead Nokia may like to position higher end Ashas as having equivalent features, but cheaper options to low-end Lumias. This will allow them to tap those customers which may like to enjoy low-end Lumia like experience but at lower price. The naming of the device conveys the position of any Nokia across the whole product range. Hence naming it 509 may certainly serve the purpose of putting it very close to Lumias in customer’s mind !!