A lot of these assertions like "the ereader is dead" are predicated upon claims that "ereader sales are going down" and "ebook sales are going down".
If you consider that all manufacturers use the same supplier for e-ink panels, then looking at the financials of that company (E-ink Holdings) should actually give a sense of what is happening in the market. See their financial reports here ->
http://www.ir-cloud.com/taiwan/8069/...s.php?t=annual
Their annual revenue is steadily increasing since they hit the bottom in 2013-2014 indicating that the market is not exactly "dying off".
Regarding the claim that "ebook sales going down". Now, this one is a bit murkier. The issue here is many of these reports do not count alternative revenue streams for ebooks like the kindle unlimited platform. See this for how the revenue stream from kindle unlimited is growing each month ->
https://translate.google.com/transla...-text=&act=url
The data is based on Amazon's own blog, where they release this information each month ->
https://www.kdpcommunity.com/s/artic...language=en_US
The publishers chose to assert control over amazon to jack up ebook prices. Amazon responded by creating a revenue stream that excludes many big publishers and is actively taking their market share through this platform.
The bottom line is that while the ereader and ebook market isn't growing as it used to, it is not exactly dying either. There is also a lot more accessible entertainment alternatives for consumers choosing to spend their money these days compared to even ten years back, and the net effect is increased competition to fill their "free time".