There seems to be a movement that has formed the last few years that push hard copy books over digital books. I can't tell you how many people in this camp have said things like "You just can't replace the feel of holding a book" to support their stance that physical books are better than ebooks. Primarily, they are people in at least their forties that might be resistant to change.
I think the push to go back to hardback books is a fad. I think ebooks will still become more of the norm eventually, but hardcopy books will never go away, either. But I do think hardcopy books will primarily be bought for kids, or for books that you want to keep forever, like a bible.
I think the fact that we see less and less of the Watchtower printing literature just follows the trend we see anywhere. Even in public schools in America, there is a push in schools for digital textbooks to replace hard copies, and that has already happened in a lot of districts. At the same time, I absolutely believe the Watchtower is going to digital literature because of money. Since when has the Watchtower EVER embraced a new technology and changed with the trends of the world? Never. The only motivation left is to save money.