It's never been easier to produce physical books. With a little online research, anyone with an Internet connection can now self-publish a book for only a few dollars.
As a medium, printed matter's value in tomorrow's market is mainly as a lovable and portable artifact. Accordingly, physical books and magazines will make the most sense, and have the most value, when used as a medium for high-quality content which justifies high production values.
We may also expect to see a re-stratification of content between the printed matter and digital mediums. Only those publications whose quality creates enough demand to support the investment needed to generate printed matter of sufficient value will recognize gains by offering that printed matter. Meanwhile, lower-quality self-publishing activity will shift increasingly to digital media as the market for cheap self-published paperbacks evaporates and the market for cheap self-published ebooks expands.
If this is the case, there is a danger that prosumer-style self-publishing print services like CreateSpace and MagCloud will begin to fade away or reorient themselves.
Currently, however, these services exist, and the back-end tools necessary to generate PDFs have also existed for some time. Assuming CreateSpace or MagCloud could be convinced to expose an API, all that a Publishing Everywhere system would need is a UI to configure the generation of a print-quality PDF, and you would be able to click a button and land printed books or magazines on your subscribers' doorsteps.