the best we can hope for is two things.
one is that pirlo can ignite the hunger and fire back into the old guard (bonucci, sandro, chiellini depending on his condition)
and the other is just like conte, inzaghi and gasperini, he can make his players, even the average ones perfom better as part of a unit vs their own individial quality ( rabiot, arthur, milik if he joins)
that is best case scenario. problem is that you sometimes get lucky with coaches like conte that bring out the best right away. but in case of inzaghi and gasperini it was many years of being in charge before we saw their current monster teams. will we have patience to wait? i dont know