For the time beeing, the sales of books have not really suffered from the competition of the electronic delivery systems. In Europe as in America, the figures for 2009 don't show a sharp decrease. E-books are still a limited offer and, fortunately, piracy has not reached the scale of video or music.
Still, I would like to try to look forward. What will happen next year or, a bit further, lets say in 2015?
I believe one should draw a line between fiction and non fiction. As far as fiction is concerned, I don't think things will change dramatically. A paper book is easy to carry, easy to use. Electronic readers won't replace them so quickly and so easily.
Things look very different for non fiction. It is already a common practice to use smartphone applications or research systems like Google, to get for free or at a minimal cost, massive informations on every topic. Yes but people enjoy grasping a synthetic view through an exhaustive book. Is it true really? People don't like to waste their time, especially when they work outside of the literary field. They get used to Internet for their job or their studies. Why should they behave differently for their own leisures ?