E Ink has announced their next-gen display technology called Pearl, to be released in July 2010. This new display has about 50% improved contrast ratio compared to the current Vizplex displays. The Pearl has 16 levels of gray, improved power consumption (and of course they do not require power when images are not changed).
The Pearl is the display used in Amazon's new Graphite Kindle DX, which will ship on July 2010, and cost $379.