I think the article is essentially right - 50 years from now there probably won't be any dedicated e-readers, but something that can duplicate the easy reading screen with the other functionality of the iPad (and probably other stuff we can only dream of. And hopefully buttons).
But until then, something like the Kindle will have the advantage of being more readable and now, being far, far cheaper. The $139 will lead to it being adopted more by average people, as opposed to well, the sort that read the NY Times.
Heck, at $599, the iPad is really competing with laptops, not e-readers. And laptops do oh so more (to the ipad what the ipad is to the Kindle)