Well, I own both books and an iPad, and I use both. I very much doubt that hardcopy books will ever entirely disappear, just as the invention of the typewriter did not do away with pens, pencils, and paper. But this is certainly another change of medium and it seems that every time it changes, there are people around predicting the complete death of the older media. How it will turn out in the long term, only time will tell.
I do see one upside to the massive OED becoming electronic: people will no longer be able to claim they didn't have access to a decent dictionary as an excuse for chronic misspelling due to laziness.
