As of late, there has been lots of speculation that hardcover textbooks will fall pray to the digital revolution and ebooks will eat away at sales until publishers give up completely. However, it's a big industry, and there are reasons why hardcovers have stuck around this long. I don't foresee a complete switch to ebooks, but many publishers are discoutinuing some hardcovers in favor of digital copies. If it does happen, it will be gradual.
High Schools Can't Switch to Ebooks
This is more about economics than anything else. Public schools provide textbooks to students free of charge - they have to, and they reuse them over and over again. Those schools cannot provide iPads to students every year, nor can they ask parents to provide them. One printed book can last years, so long as the information doesn't change. I don't see public school ever switching to ebooks.
Students Can't Resell Ebooks
Since digital content doesn't age like paper, it's impossible to sell a "used" ebook because there is no such thing. Students would be on the hook for the full, new price of every etextbook they required. The cost would be less because there wouldn't be any associated printing costs, but it would still be super expensive. If this happens, it won't be saving students any money. Young people needing an education are cash cows for too many industries - banks, universities, the textbook industry, housing, apartments, etc.
Many Students Prefer Physical Books
A lot of people like reading physical books as opposed to ebooks. Maybe it's the feel of the books in one's hand or the fact that you can't read most ebooks outside in the sun (unless it's on a Kindle). Students also like to mark in their textbooks, make notes, and highlight - I've done this with many of my books over the years. It's possible to highlight in ebooks, but it's not the same.
If you want to sell your textbook at the end of the semester, it's generally a good idea to keep highlighting to a minimum. Most buyback companies will pay you less if your book arrives looking like a christmas tree.
It has been argued that high intensity, blue light is bad for peoples' eyes. Whether it is or not is up for debate, but staring into LED bulbs can't be good for one's eyes - that's what a computer screen is, a bunch of led lights spread out. We just don't know how a lifetime of staring at screens will do to someone's eyes because they haven't been around that long. Reading print books won't cause you any blue light worries.
I believe we'll see a gradual shift to etextbooks in some subjects/classes, but I don't think it will be a complete switch. The textbook industry is just too big, and there are too many companies involved in producing, selling, and reselling used books. A switch would cut into their revenues too much. However, it's hard to predict, and it may happen if companies find ways to monetize etextbooks to the extent they have print editions. But it won't happen unless students start preferring reading their material on a computer screen as opposed to a piece of paper; it may take many years for that to happen.