I'm surprised that nobody referred to the Kindle Chronicles pod cast that Len Edgerly runs every week. Last friday's interview was with Sri Peruvemba, Chief Marketing Officer for E Ink Holdings, the supplier of the ePaper technology used in the Kindle and other leading e-readers.
In this interview, Sri clearly states that the display used on the K4 is the same as the K3. Both are Pearl display of the same vintage.
Interesting interview. I encourage you to listen to it.
http://www.thekindlechronicles.com/2...sri-peruvemba/