I don't think this is a death knell for D&D, and worries about that are an overreaction. Similarly, I think the lack of compilation is definitely a shame, but has pretty much nothing to do with this being the "end of Dungeon and Dragon" - if they keep coming out with quality articles, that's all that is needed.
That said, I'm definitely
disappointed in all of these announcements, especially with so little good news to soften the blow. The increase in free content on the site in the form of weekly articles is nice, and the enhanced editing process is important. But we'll see how well it comes together.
The Class Compendium
Seems like there were quite a few people looking forward to this on this forum, but from my understanding this was basically a reprint of existing classes + errata. The completist in me wants that, sure, but my practically speaking its not something most of us need.
The main elements that were going to be in here were rules for how Essentials classes worked with multiclassing and such. Now, I don't think it needed an entire book for that, but it would be nice to see that content somewhere.
Mordenkainen's Magnificent Emporium
So despite the cool name, my understanding is that this was basically going to be Adventurer's Vault 3. I never found the first two that interesting, personally, and I've heard they weren't big sellers.
I think the first one was. This one seemed more important because Essentials completed overhauled the magic item system. Right now, the rarity system is pretty much incomplete - this book promised to fill that gap. Without it, WotC has kinda left DMs to try and patch the game themselves, and that's unfortunate.
Hero Builder's Handbook
Actually, I don't even know what this was supposed to be. Sounds vaguely in the line of the Player's Strategy Guide? Anyone?
This was probably the 4E book I have most anticipated. I don't think it was a book with build advice like the PSG, but instead a book with a lot of innovations. More themes for universal use. Rules for non-combat element. Etc. We didn't know too much about it as yet, but it sounded very promising. I really hope we'll see that information show up somewhere, without too long a wait.
I am very disappointed that the books have disappeared, but haven't given up hope yet. The optimist in me says that WotC is backpedalling on the direction they had moved the RPG content in - following Essentials, we saw a whole host of new style books, rather than the "PHB1,2,3, DMG1,2,3, Martial Power, etc" that we had gotten used to. From what I've heard, Essentials was successful, but not the amazing hit they may have been counting on.
I'm hoping we will see a return to the earlier format, and some of this material harvested for it. But honestly, no way to be sure. WotC is clearly focusing on the non-RPG building of the D&D brand, which I think is a good thing. I just don't want it to come at the cost of the actual RPG content, and hope they get their strategy together, and sooner rather than later.