Amazon CEO Jeff Bezos answered a couple of questions in the USA Today about the new Kindle and also on eBooks in general.
The most stunning statement of Jeff Bezos is: "I predict we will surpass paperback sales sometime in the next nine to 12 months. Sometime after that, we'll surpass the combination of paperback and hardcover. It stuns me. People forget that Kindle is only 33 months old."
Bold statement, but based on recent new that Kindle eBook sales beat hardcover sales this month, I'd have to say it's doable.