There will never be such a gizmo with the catchy title PRS-T4 and the Sony Reader PRS-T3 will be sold until it runs out. Since that was launched last autumn and only in the EU, Sony could not have have many left.
Sony pioneered the idea of an E-ink ereader in 2004 when it launched the Sony Librie in 2004.
The company worked with E-ink and Toppan Printing Co of Japan for several years to develop the first generation of the 6″ screen which was used in the Librie, and later the Sony Reader, Kindle, Nook, and other ereaders.
Sony released the first 6″ screen, it also followed it up with several cutting edge devices. It was also the first to adopt Epub, and to combine an E-ink screen with a touchscreen and a frontlight.
But Sony was largely aced by the Nook-Kindle price war in June 2010 and lost out in the price drop that followed.