The radio/TV comparison is a little off. Radio is a fundamentally different experience than TV: it doesn't require sight. So that allows it to occupy it's rather substantial niche.
Paper books still have some interface advantages over ebooks (as several people have described in this thread) but they'll go away as people build proper, well designed ebook readers.
When that happens, all books will have going for them is nostalgia and a pleasant physical experience that can't be replicated digitally. I think a much more apt comparison is records, which don't provide a fundamentally different sonic experience, but do have nostalgia and physicality.
So I think a handful of book lovers will still have collections, and visit the bookstore down the street, but like record players, and unlike radios, I think the vast majority of the population won't have any.