If any portion of a planned development district that can be developed remains substantially undeveloped three years after final approval, the Town Board may rescind the approval, in whole or in part, following a public hearing. Upon petition and with cause, the Town Board may grant a one-time extension, not to exceed four years. In the event the Town Board rescinds an approval, the Town Board shall at that time reclassify undeveloped lands in the district based on the zoning regulations in effect at that time. Developed portions of the planned development district may either be allowed to retain the planned development district designation or reclassified based on the zoning regulations in effect at that time.