A very speculative model which we have yet so see emerge is the development of book production 'content production markets'. Code development has had this for a long time with sites like freelancer.com where project managers can find free lance programmers. Project managers post specific jobs to freelancer.com and programmers make bids for the work. The Project Manager then evaluates the bidders experience and client feedback against the amount the bidder posted.
It is very easy to imagine that this kind of business could evolve for book production. There are many people in the world with skills relative to book production that can be executed online - editing, writing, illustration, research, fact checking - you name it. Development of a formalised and informal trading of these skills could create significant revenues for participants and could really explode the current book production model and the revenues available for producers.
I believe there is a business here - either customising content as a service or providing the tools for people to customise heir own content. It is also very possible that one book could in itself provide a lucrative 'long tale' business if the tale was long enough.
Some are putting their money on the sale of book components - selling parts of a book, typically in chapter form. This necessitates closed copyright as a rule. OReilly have been experimenting with this for about 5 years and it seems to be their darling. The newest iteration being the Inkling project which is strongly backed by OReilly. Inkling markets educational material in chapter form.
I think this is a very interesting strategy but I don't like it because the sale of content like this always works against reuse and collaboration. If the bottom line is still in resale of the artefact this will always work against free culture and movements like the Open Education Resources movement. From this perspective this process is flowing against new forms of education processes. I can't help but be cynical to think Inkling will make more money from a single book through chapter sales than they would ever make from selling the book as a whole. If you look at some of Inklings titles and total up the price per chapter against the total number of chapters then it is apparent the cost to the buyer exceeds the cover price' of the entire book. Its a cynical move. Real innovation in this field would construct markets for chapter production with the contents being free to distribute and reuse as mentioned above. Unfortunately chapter resale in the form that OReilly and Inkling pursue is going to have a successful market but its working against more enlightened approaches to education and the future of the book in the long term.