my bet is it can go both ways.
Cheap devices based on flexible e-paper, and expensive devices based on color e-ink.
Though these devices will not be popular, because of their low battery life.
Look at the Jetbook color,
it lasts only a few weeks on a charge, and that's despite the huge battery it has.
I think there will be more technology break troughs, like a capacitive TFT screens or so, where the battery life can be extended while performance goes up, kind of like where Pixel Qi was working on for so many years already...