Let's just focus on books, yes Amazon sells other things but we are interested in books.
The way that Amazon will continue to exist in the ebook distribution realm is by offering better incentives for authors to upload their books onto Amazon's servers. Amazon is a
machine(I haven't read it yet but I might), maybe that means they will be more efficient at distributing books and will be able to exist on smaller profit margins, it is expected that all profit margins will approach zero as we move into the new era.
But Amazon has also recently tried to lure authors into its inner machinations with the promise of large advances, to me this implies a conflicting ideology and will probably need to be reconciled in the future.
The publishers and Amazon are doing the same thing, marketing books. It just makes sense to cut one of them out.