Heck, I still buy hardbacks, if I have a good coupon or other discount, or if the book isn't available in e-book format. But sometimes I look for the e-book now.
Maybe publishers should start putting extras in the hardbacks, in the same way movie studios load DVDs with everything from commentary and deleted scenes to free T-shirts. Or heck, learn from Baen and include CDs with the hardbacks. (Buy the hardback and get a free e-book. Or so.) If they want sales to go up quickly, then they can include them only with the first printing, or only with the first thousand books, encouraging people to buy the hardback more quickly.