The note in the back of AFFC says specifically that ADWD "wasn't close to finished yet," (direct quotation) and that it "will be along next year, (I devoutly hope)," (direct quotation).

It was an expression of hope that was then supersceded by other events (the decision to rewrite significant amounts of that material).

Even if reliance theory was applicable, would it not also apply to the quality of the work? Because if ADWD had been published in 2006, it would have been an outstandingly weak book (based on the sample chapters available at the time) and people would be complaining at length about that.

As for the other point, even if ADWD had come out in 2006, there were still two more books to come, and we'd still be waiting for them even now. There never was any promise of completion of the whole series in the 'near future', certainly not in 2006 and not now either.