Print materials such as books and magazines are limiting by their very nature. You can’t search them easily; they are not easily updated; and distribution has a big impact on sales. I predict that in 10 years books will be viewed as an inefficient and antiquated way to consume technical content by the mainstream. David Stutz is often quoted for writing:

Software written above the level of the single device will command high margins for a long time to come.

I believe content written above the level of a single book (or magazine) will also command high margins for a long time. Content should be treated as one big online library that can be easily searched, browsed, and tagged so you can find exactly what you want without being limited by the pages of a book.

Also, since writing a book is such a significant undertaking, many qualified people never attempt it. By focusing on smaller units of content instead of just books, I believe there is a long tail of authors that will emerge to contribute valuable content.