I'm not sure that's a given.
The environment *is* challenging for competitors but there is room for alternative readers built around something other than ebook storefronts. Competitors do need to understand that if the want to compete they *have* to compete; they have to establish retail presence, let consumers know what their value proposition is, and make sure they offer more than just a minimalist reading experience.
In the new regime it's not enough to announce a reader, put up a website, and sit back to wait and see if anybody nibbles. Online-only "Fly-fishing" marketing won't do when there's trawlers out there. And it would help if (some) vendors remembered that there is such a thing as post-sale support.
Not going to be easy but, if quoted numbers can be believed, there's still 30-million customers up for grabs in the US alone. There should be room for something besides the connected-storefront readers.
We can hope.