I dont think they will force anybody. They will just make the book items available online for folks who prefer them. Which these days is many.
As someone who uses DDB a ton, I don't see them forcing anyone to swap to DDB, at least not by stopping production of print books. Why would they do that when there's still lots of money to be made in traditional media?
Instead, they are making DDB really, really good value. So it is very enticing, particularly for younger players, those who play online, or those managing a bunch of different campaigns. Books are basically half-price, with regular sales on top of that, and with a DM-tier subscription you can share as many of them as you like with all of your players. Then there's all the features that make running the game much easier, like the Encounter Builder, searchable magic item and monster archives, character creator, and, most recently, the integrated maps.
I think there will be a profitable market for print media for the foreseeable future. But DDB will increasingly become the go-to tool for running games, often in conjunction with print media.
Edit: I also think that we can't have a meaningful discussion about what editions will look like going forward unless taking into account that the game is now built around DDB. Anyone suggesting a radical rules revision: it ain't going to happen. We might see significant change over time, in increments, but they aren't going to make any changes that break DDB and make my library obsolete overnight, like a 4e to 5e switch. It's just not a viable strategy anymore, if it ever was.