Like the Internet, the Web is a terrific solution to a nonexistent problem. Someday we will find problems that the Web will solve. It follows from a sense of economic principles that publishing on-line is cheap. The cost of paper is skyrocketing. A curious phenomenon is that every year, publishing on-line gets cheaper and publishing on paper gets more expensive.
Bad money drives out the good.
The Internet is the land of the cheap, the home of the free. I suspect that rather than ending publishing, the Web and the Internet will take the lousier manuscripts out of the bookstores and put them on-line. Good authors will continue to publish real books. Somebody else will swipe them and publish them. It happens in science all the time.