I think it will always be a trend, for companies like Barnes and Noble I'm guessing they just couldn't wait for color eink. As great as a tech eink is, it's evolving at a snails pace.
eink has been out for quite a few years now and the best thing that has every one hootin and hollerin about is the "Pearl Screen"? So basically everyone is popping champagne corks because the screen now has a little bit better contrast ratio?
eink really need to pick up the pace.