If I hadn't bought the PH3, no way in hell would I try to understand what an ardent or psion does based on a reading of DDI. It's basically not a friendly way to gain information- it's a pain in the ass trying to put the pieces together.
Which is why putting new classes with all-new mechanics that need to be explained on the bookshelves makes sense, and I wouldn't say they would (or should) stop doing that. But Psionic Power? Where the only "completely new" information is perhaps a new build class ability? That could easily appear in a Dragon Magazine article with little to no fuss. And if this new build was only to appear via DDI... it would inspire more people who want that information to actually buy a subscription, at which point they'd experience what they'd also get from the RC, CB, MT and VTT.
I think moving to an increasingly electronic form of distribution is a terrible mistake, because WotC doesn't seem to be able to handle their current electronic offerings. Why on earth would I have faith that moving more and more stuff to their least successful (in the sense of "easy and fun to access and use information") channel will improve anything?
Now this is completely different. You're not arguing that they shouldn't do it because it doesn't make financial sense to do so... you're arguing they shouldn't do it because you personally don't like how they've done it previously. But that kind of personal opinion on your part will have very little influence on whether it will continue, because for every person like you who hasn't liked how they've done their digital projects in the past, there's a person like me who's been quite happy with the online tools I've been getting since being a DDI subscriber. So our personal opinions on how they run their business cancel each other out. Thus it goes back to WotC's feeling of what makes the most financial sense for them to run their business in the future.
Certainly, this isn't D&D's death knell, but it's looking like the death knell of many people's willingness to spend money on D&D.
Just like every other change that has occurred over the lifespan of the game. Every change loses someone who doesn't like the change, and their hope is always that someone new comes in to take their place. And losing one person who would buy three hardcovers (which produces only a small amount of cash for WotC) and replacing him with one person who will buy a DDI subscription (which is almost all funneled directly into the company) is a good change in the long run for the financial health of the company.