There aren't any press images of the new Paperwhite yet, but TechCrunch does have word the eReader will have a 300ppi display which will enable it to compete better with Kobo and the like. The current Paperwhite has a 212ppi display that doesn't compare well to the Kobo Aura HD.
Hardware-wise, the new Paperwhite will be packing a rear power button, chamfered edges, glass screen, and an ambient light sensor to adjust your readings according to the light in the room. The light is said to adjust gradually in order to be comfortable on a person's eye in the dark.
News of an upgraded Paperwhite comes just after the second-generation was released. Amazon announced the newest Kindle Paperwhite on 3 September, and the Wi-Fi version was released in the US on 30 September 2013 priced at $119 (£74) ad-supported and $139 without ads, and the 3G/Wi-Fi version on 5 November 2013 ($189 ad-supported, $209 no ads).