That would depend on your rate of descent. In a normal descent, where you retard the throttle but keep the IAS constant, to obtain a ROD of about 500 ft/min, nothing special is going to happen. The governor will simply use the available blade pitch range to maintain the set RPM.
But if you do a full power vertical descent, I can assure you that the coarse pitch stops will be reached very quickly indeed. This will result in the engine overspeeding, as the governor doesn't have enough blade pitch authority to keep the RPM in check.