Re: "[auto-tune]...may well end up producing a generation of singers who actually have very stable and accurate pitch"

That's true if "accurate" means notes that perfectly match the tempered scale. None of the pitch-adjusting programs I've heard of include the option of other systems of intonation of the major scale. So the resulting generation would, in theory, end up unable to sing notes that can make barbershop chords ring.

A sad day should it come to pass!