I am one of those that said that I don't buy crunch-based splat books because of DDI, although with the change to online only that throws a bit of a wrench into the works.
It may be that moving all crunch material to DDI will both increase subscriptions and sales of those books that they do publish - people will still want to buy books, after all.
The one big flaw in this hypothetical plan is the bad PR of strong-arming people into getting a DDI subscription which may result in more Pathfinder defections (actually, the thought crossed my mind as a serious option just recently).
Don't get me wrong - I for one do like having a comprehensive online source for all statistical material in the Compendium and the Character and Monster Builders but not at the expense of actual books, or at least the core rulebooks and setting/theme books. There is no substitution for a Player's Handbook or, more recently, a Rules Compendium. Call me old-fashioned but I like my books; I like pushing my desk chair a few feet in the direction of 7:30 and reaching for one of the 350+ game books on my shelves.
Books will not be fully superseded by newer technologies, imo. They may become more of a luxury item, but a book is not equivalent to a vinyl record or an eight track or a cassette tape or a compact disc. A book is a classic human object, like a violin or a candle. There are newer forms of making violin-like sounds or creating light, but people will always play violins and light candles (and read books by candle light). Again, maybe not on the same scale - the we will see more and more ebook readers on subways rather than disposable mass market paperbacks, but we're always going to have collectible items, hardcovers, and a wide range of books. I hope, at least!
This is related to what I feel is yet another misunderstanding on the part of WotC: most people that pirate PDFs don't do it at the expense of buying the hard-copy; in fact, what ends up happening is that they can better preview the material to decide whether they want to purchase the books. In this sense I never understand why WotC charged as much as they did for PDFs - their prices were why no one was buying them, not the existence of pirate copies; in fact, the prices partially drove people to the pirate copies - why spend $20 on a PDF when you can get it for free? Now if they had simply charged, say, 25% of the book price for PDFs--like an unnamed better-run companies does--they might have avoided the PDF/piracy debacle, partially through encouraging customer loyalty but also through recognizing the simple fact that a PDF costs a lot less to produce than a hardcover book. Instead WotC found a way--one of many, it turns out--to distance their fans.
