Who knows what the long term prospects for eInk based ereaders are? I'm pretty sure that a lot of the people who bought the Fire did so because it is a frighteningly cheap tablet, at least compared to the competitors.

Long term prospects though? That can go either way.

Yet I think that there are two things that we can be certain of: the Fire (and similar devices) has and will continue to push down the price of tablets, and that eInk will continue to be a strong contender for heavy readers until better technologies are developed.