I have a very nice tablet which I haven't used in 4 months. I haven't used my eink ereader for perhaps 45 minutes
Perhaps the market has saturated but I doubt it as I seem to buy at least one a year and none of mine have broken. They just get a little better (and cheaper).
Still IMO the market will likely flatten out. The improvements that are likely to happen short term are viewed by many as slight embellishments, not necessities.
Smaller size, lighter, better resolution, better firmware, better battery life will prompt a person like me to buy a new one, but I was just as happy reading on my PRS-600 as I am on any of my newer ones,
Helen