I'm not entirely convinced that the equation is that simple - this is Joss remember and any time something looks clear-cut he'll twist it around. I suspect that there will be more and more problems with slayers like Gigi and others who will take advantage of all their abilities to become Olympic gold medalists or misuse their abilities to threaten and extort money from others, for example. As a result of a rising wave of this, Buffy will have to act.

My very very long-term view of this is that it will tie in with Fray and in Fray's time there are no slayers (and haven't been any for 200 years) until she is called. My theory was always that Buffy realises that calling all the slayers is a disaster and unmakes them all (including herself?) straight after she banishes the last demon.