Mike Shatzkin of the Idealogical Company is a publishing strategist whose thoughts have been recommended here more than once. He tends to make them publicly available, and you can find a list of most of his thought-provoking presentations on the company's web site.
The text of Shatzkin's latest speech has been available for a month or so now, but I have only just got around to reading it. Unless you are very keen on reading stuff on screen, I suggest you print it out. It runs to 21 pages.
The title of the speech is 'The End of General Trade Publishing Houses: Death or Rebirth in a Niche-by-Niche World.'
You can, of course, skip this reading duty if you're just a plain old buyer of books (though what Shatzkin has to say will affect you just as much as anyone else). But if you're planning any sort of business or professional association with the book trade in the next decade or two, I suggest that you give Shatzkin your attention. He doesn't offer an infallible road map into the future, but he will at least get you thinking about how the book world is changing.
If you want a brief summary (dangerous thing), then Shatzkin suggests that general trade publishing will dwindle away, and that publishers will instead cater for much more tightly defined niches in the market than they do at present. And that doesn't mean setting up more imprints (remember Nelson?).
And there's wonderful (?) news for authors. The preponderance of agents, says Shatzkin, think that authors should spend 2 to 10 hours a week promoting themselves online. What fun, eh?
Here's a hint for writers just starting out. Probably the main reason why my 'career' as a writer never got very far was because I never found a tiny niche and stuck to it. I always liked to do different things: mainstream novels, thrillers, police procedurals, all sorts. I also wrote for several different media: books, stage, TV, radio. Hence no big-time success. But I had a lot more fun doing that than I would have had if I'd gone down the niche route for the last forty years.