I think paper books will stay if only for the joy of dealing with them (not the mass market paperbacks, of course).
Flipping through real pages is much more satisfying than using the ebook readers' navigation widgets.
For mass market pbs at least you don't need to worry about your device on the beach, be it stolen or wrecked by UV-rays, sand and salt water.
Acid free paper books are more durable than any digital medium. You do not need to follow new hardware media generations because no disk, tape or whatever drives are needed.
An analogous copy of really important documents will always be an indispensable backup.
Paper books don't need electricity, even if the Sun stops shining
Paper books which show some craftsmanship like a beautifully bound and printed 15'' artbook touch my soul. It's not the content alone.
I cannot imagine to read graphic novels or French B.D. style comic books on a screen.
And finally, because I don't want that paper books disappear.
hansl