1. The design of devices on which to read eBooks are far too bulky, non-ergonomic and expensive. Until 13" tablets are ultra-light weight, malleable, full color, and have extra long battery life, at a reasonable price, the medium will play second-fiddle to the comfort of a real book.
2. eBook ownership is confusing and tied to particular companies which exert authoritative control over one's library. Having to recollect the particular app to open to find a particular book sucks. But worse, the horror stories of cancelled accounts and subsequent loss of all purchased books will keep any thinking person away from anything more than cursory purchases.
Fix these two problems and the eBook deluge will really begin. Until then I wouldn't even be surprised to see a drop in sales.