On March 6, 2018, the Starwood Preferred Guest annual category changes will take effect. The breakdown is that 276 properties are being affected.-9% are moving down one category and 8% are moving up one category.
Will this affect that redemption that you have had your eye on? If it will affect you negatively, you should act before March 6 and book your rewards redemption. If the amount that you need to redeem for your award will decrease after March 6 (wishful thinking), you should wait to book your reservation.
You can review the list of changes scheduled to take affect here.