Answer
Increases.
Work Step by Step
After some time when we add solid $KI$ to the solution, it achieves equilibrium (saturation) again. This means $[Pb^{2+}][I^{-}]^2$ once again equals $Ksp$. But this time, because $[Pb^{2+}]$ has decreased (proven in 17.60b), $[I^{-}]$ must become larger so that the product would be big enough.
