Also, I play both 4e and 5e, and am working on a set of modules and house rules for 5e that make it play more like a streamlined 4.5e.
if I was demanding a campaign and players guide for each published setting, I'd understand the reaction some people have. And in the case of DL, I get that what sets it apart isn't very mechanical, so I get that argument hat it doesn't need an update, but I don't really want the old books. I want a new setting writeup that makes sense of the setting, and moves the setting forward a bit to bring it full circle to the "feel" of the WoTL, but with the PCs set up to be the Heroes. The old books are there for playing in older eras. Just give me a solid timeline/history, and then info on where everything is after the last novel, and move some things forward to bring it full circle.
Ie, create a miracle in the face of impending darkness that has the chance to give the world hope again, and place the PCs in a position to go out and save the world. Maybe the great trees of Solace magically regrow, complete with buildings in their branches, over night. And the heroe's monument/tomb thing opens, and...here's an adventure that sets the party on the path to saving the world.
Could be a small suppliment in an online article, or if they are willing to invest a bit, get Weis and Hickman to team up with the wotc team and make a full storyline of it.
Or don't. Just do some subclasses and race options, and some monsters, and make the old books printable.
anyway, I did appreciate Mearls answering the question on twitter.