The wire will equalise the potential between the contact points on the insulators. It cannot do any more than that, because the insulators will not conduct. Because they cannot conduct, charge cannot flow from other parts of the insulators, and hence they will stay at their original potential.

The wire will equalise the potential between the contact points on the insulators. It cannot do any more than that, because the insulators will not conduct. Because they cannot conduct, charge cannot flow from other parts of the insulators, and hence they will stay at their original potential.

EDIT I should add that there is no such thing as a perfect insulator. All substances conduct some current. We call it an insulator when the conduction is negligible. If the voltage is high enough, a conductor will also "break down" and start conducting.