1) The future of reference works will be online, because research requires the aggregation and association of divergent pieces of information. For dictionaries and encyclopedias of all sorts, there is — and should be — no going back from the hyperlink. It is almost impossible to imagine that there will be another printed edition of the Oxford English Dictionary for example. (For a discussion of that point, see this post — scroll down to “Day 2” and follow the links.)
2) As long as e-readers continue to promote linearity of attention — as I argue the Kindle does — they will increasingly be seen as the natural home of narrative-dominated books, whether works of fiction or history or current events or true crime or whatever. When a book is written in such a way as to encourage you to keep turning the pages, keep moving forward in the story, then the e-reader will seem an appropriate medium for that book.
3) This means that the traditional printed book will be the best home for works that need to be lingered over, meditated, considered with care. Literary fiction, then — I wouldn't want to read Marilynne Robinson’s Gilead or Home on an e-reader — and poetry, and any book that depends on fine illustration. Most works of humanistic learning, of serious scholarship. As a professor of English, books such as these constitute much of my reading life, so I don't see the Kindle, as much as I like it, becoming anything more than an ancillary device for me. But if e-readers do come to be more and more prominent, as I expect they will, then what will become of these kinds of work that (so I claim) are best experienced the old-fashioned way? Will readers learn to be more contemplative while reading such books on e-readers, despite the promptings of the technology to move them forward? Will writers gradually learn to adapt their own styles to this more propulsive medium? Or will works that fit the technology of the printed book simply decline in prevalence and importance?