I got the impression that the new screen wouldn't add anything noticable to the cost of production. It was mentioned a few times that whilst there's going to be newer tech that provides colour eInk displays, it'll require a change in manufacturing where as the pixel Qi is supposed to be manufactured on very similar production gear. So whilst it may not be able to compete directly when the newer display tech comes around, it's going to be on sale sooner and should be cheaper.
The
PopSci post covers some of this.
Next year or two looks to be bringing some interesting changes in display tech
