Update: Ken Edgerly of Kindle Chronicles has a video, the only one I have seen, comparing the 2nd generation Paperwhite, 3rd Generation Paperwhite and the Kindle Voyager that I think is helpful to seeing what is actually changed.
Amazon quietly announced a new Paperwhite this morning. The new Paperwhite follows up on the original Paperwhite in 2012 and the second generation released in late 2013.
The 2015 Paperwhite keeps the same physical specifications as the first two Kindle Paperwhite generations and the same price.
The main differences are that the new Paperwhite has the same screen as the Kindle Voyager (300 dpi up from 212 dpi) and doubled the ram to 512 MB. The battery and storage space remain the same (and quite adequate).
The other differences are software. The new Bookerly Font that was released on the iOS apps recently will now be native on the Paperwhite. Also there will be a new layout engine that will more closely match the way print books look.
Evidently the new typeset engine will allow the word “quietly” to have the tail of the y that wraps slightly underneath the l. I am all for making these design changes to the Kindle and making the process of reading electronically more elegant and natural.
But this is not an essential upgrade for anyone that has a working Paperwhite. What it does do is make the Kindle Voyager less appealing. The Voyager is $90 more expensive and apart from a light sensor, page turn buttons and flat glass screen, there is now no real difference from the Paperwhite.
The main feature that I think would be useful is to make the Kindle waterproof like the Kobo H20. You can buy a waterproofed Paperwhite from Waterfi, although they have not publicly announced that they are using the new paperwhites yet. I did ask them this morning if they had plans to upgrade anytime soon, but have not heard back yet. Waterfi has not started offering the Voyager (probably because of issues around the buttons.)
The new Paperwhite comes out June 30th, and I would expect that refurbished models of the older Paperwhites will be on sale soon.