It is not obvious to me that it has to.

Books are technically obsolete, but there are still plenty of cases -- stundents going to exams, book that depend on exact layout, etc -- where ebooks are no substitute.

An the skills in marketing, layout, editing, etc that the publishers have build up over the years are as needed now as they have ever been.

The only way the publishers will fail is if they don't adapt.

And even then, people are still selling horse drawn buggies (http://www.buggy.com/ -- warning early 90 design) on the internet.