I'm not sure if anyone has even connected these dots, but don't you think that the creation of the online site might be a prelude to WoTC's abandonment of printed products as a whole? Think about how much easier and proffitable it would be for them to distribute new dnd products (at full cost) if all you have to worry about is bandwidth and not the cost printing, materials, overhead and physical distribution.
Now imagine how much more profitable it would be for WoTC if the only way anyone could obtain previews and errata for these products are by subscribing to an online website.
Is online content distribution profitable, hell yeah.