It's an old prediction going back to the roll out of e-readers, and it's a compelling one, I suppose. E-readers can hold an entire library of books stored on the device itself, or in"the cloud." They are convenient, and easy to use, and have some advantages that physical books don't. E-books don't lose their bindings, or have pages to rip, or fade with time. And, more importantly, if you're like me, and like to have a variety of books on long trips, vacations, or just in case your mood changes or you finish one before you get home, the number of choices in the palm of your hand are limited only to the number of books stored in your "library. Most readers even have a backlight effect so you can read at night in the dark."
With all that going for them, it's easy to see why some people feel there's no longer any need for hardcover or paperback books. But disappear? Nah...I don't think so. Having a new way to do something does not always mean "sundowning" the old way. Television didn't replace movies, after all, and even vinyl records are making a comeback. There's just something about the feel of a book in your hands, the weight of it, even the smell of it, that no e-reader or book can replace. I love sitting in my workspace and being able to look over at bookcases overflowing with well-read volumes. Just seeing the title on the spine of some of these often brings back the pleasure of the first time I read them. Call it romanticism if you will, (or nostalgia, I guess, if you're one of those who've moved on from physical books) but there is an intimacy with physical books that you just can't get with e-readers.
Now, don't get it twisted. I am no Luddite, even when it comes to my reading preference. I have a Kindle app, and I like it just fine, thank you very much. I've got a whole list of books stored in it, some of which I've read, and some of which I am very much looking forward to reading. But...books, though.
Still, I do acknowledge that there is a shift in the publishing paradigm. Physical books will never go away, IMHO, but if you're a writer, you'd better pay attention to that shift. With many publishers, especially magazines, more interested in publishing electronically than with getting into brick-and-mortar stores, or, at least equally, you would do well to familiarize yourself with the legal definition, industry standard rates for royalties, and even the different forms of contractual language involved with electronic rights (they may not be specifically called "electronic rights;" The contract could just refer to "any and all media and formats," or some such), and acceptable contract terms for same, or you may end up wishing you'd paid more attention to the fine print.