The next step will be that authors will sell to readers directly; that will disintermediate both publishers and Amazon, and there's no reason it should not happen.
(It's easy to lose sight of, but the entire world does not consist of people similar to HN readers gearing up to launch a new startup. Not even close.)
By getting rid of the middleman, the authors will be taking on the new challenge of marketing their books- by no means an easy task, especially if you are unknown and not tech-savvy.
Note that while I work at Lulu, I don't officially speak for them.
The new generations of authors will be very tech-savvy, to a point that may sound incredible now but is very real.
And even if some, or the majority, of authors don't want to do this themselves, why can't they hire a bunch of folks to do it for them? Why would they hand over 70 to 85% of potential returns to a publisher or to Amazon when they can pay someone a fixed price for editing, proofing and page layout, and keep 100% of the returns after that?
Publishers are clearly doomed since they don't provide enough values for the fees they demand; but I doubt Amazon's position is a lot more secure.
So your example for something that could replace Amazon... is Amazon?
Amazon is doing at least two things really well that is going to be completely impractical for individual self-publishing authors to do on their own: Providing a go-to place for customers looking for books, and payment processing.
Yes! ;-) The example was used to refute the fact that authors are technically incompetent. In the next generation most people will be able to put together an ebook.
I think the threat to Amazon will come first from best-selling authors, who already have a faithful following of their own. For everybody else, Amazon is great, for now.
But imagine a future where a search engine can help you find great ebooks, and where a simple payment system can let you buy them directly from authors (charging 2-3% to authors) -- why would you need Amazon then?
You just described Amazon. On top of that, they have the recommendation engine, public wishlist, affiliate program, and allow you to buy all kinds of other products via the same UI.
It's going to be very, very hard for any competitor to become attractive enough for customers to matter. I don't think even best-selling authors can just ignore that factor.
When it follows the rules, disruption starts at the low end, competing with non consumption and its near margin. Lots of books can't be viably published via the old system but might still be viable fo self publishing. For example, a book that can expect 2000 sales.
The question is not necessarily will the established authors & publishers prefer "to write, not deal with the minutiae of self-publishing." The question is will future authors prefer to try and find someone willing to publish their books or will they just self publish? I think a lot of them will self publish.
The second reason is cost. The traditional publishing process is expensive. It's an all exclusive package that includes financing, editing, promoting and all sorts of other stuff that authors probably want to avoid but it costs. Authors earn a small percentage of the price of a book. From what I understand, it can be between 1% & 25%. That is a lot of room for improvement.