Oh I don't doubt that eventually there will be majority/all digital readers with books becoming the rarer alternative. In fact I would go as far as to say this is an inevitable change.
I just articulate my view as a personal one, I would happily be the last one left reading books because until they go exclusively digital I will continue to purchase and love books. I have over 300 books that I own and have read now, books/series that I have especially enjoyed I am slowly replacing paperback with hardbacks for longer durability (and they look nicer) I have a real pride in my collection. Nearly murdered the missus when she dared to suggest taking some to a car boot sale, I plotted GBH when she suggested putting some in the loft in boxes. They still sit proud dominating every available surface in our office
Will be a sad day when books move on to the periphery and I think the final tipping point will be when schools switch to digi tablet devices away from books. This will probably happen as well when it becomes economically viable.