An update to the above post, which either punctures the whole thing, or makes it a bit more intriguing:

Lackey responded to questions, not with a comment, but with a link to the Amazon link for The Slow Regard of Silent Things, the implication possibly being that she was thinking of Slow Regard as Kingkiller book 3, and while it is that in a sense, it is not being waited for by anyone as it was released almost 8 years ago.

One way to view this: there's nothing more to this than that Lackey made a simple mistake in confusing Slow Regard with Doors of Stone and we can all go back to listening for whispers in the void for DOS hints.

A 2nd way to view this: Lackey intentionally refrained from making an actual comment ("sorry for the trouble, gang - I know nothing of Doors of Stone") because she does in fact have the DOS info she previously related and didn't want to lie about that and/or doesn't want to start a new conversation surrounding the words she chooses for the denial (denial via Amazon link being the simpler denial).

I like the second one, but that may be because, well, I like the second one.