The problem is that US letter paper or A4 are both roughly 14" diagonal, and textbooks and magazines are often a bit larger, so you need something like a borderless 15" diagonal display with at least 300px/in resolution. I'm hoping that within a few years we'll see reasonably-priced tablets with displays like this and with serious battery life (say, 24 hours or so, because thinner isn't everyone's first priority).
The ebook format, because it doesn't make archaic assumptions about "paper size", and I can therefore read it on anything from a phone to a wall-sized projector screen.
Someone should make an online converter: you email your paper to the converter address, it optimizes it and sends it to your Kindle.
The paperwhite, however, is terrible for papers, and I don't think the higher resolution screen would be helpful. At least for my eyes, cramming a full letter sized page into the small screen wouldn't work... so I'd still be left with a view of a subset of the page.