The prices will more likely stabilize than drop. Come to think of it, If you're an owner of an 5 room HDB flat who fulfilled the MOP and prior to the Aug-30 cooling measures would you sell knowing you can rent it out for $2.8k/mo as there are more renters than buyer? No cooling measures will make the prices of HDB drop as the case is about demand over supply, in this current situation there are more demand than supply.