On March 5, Starwood will have the new Cash & Points rate for its hotels (you can read my piece about this change here) and the yearly category creep will happen at the same time (you can read my take about it here).
You will have until March 4 (likely US time) to book Cash & Points and hotel awards at the current rates. Tomorrow, the new rates will be in effect. Note that changing the dates of awards later requires you to pay the higher amount.
This is especially bad if you are doing lot of Cash & Points awards at the properties that are moving up in award categories. You will get hit by both the higher Cash & Points requirements + the change in award categories. This makes Cash & Points award less appealing on many instances i.e. current category 5 property that moves to category 6. When you combine the higher Cash & Point with category change, the new prices changes from 4800 Starpoints + $90 to 10000 Starpoints + $180. Quite a change.
If you are planning to do any Cash & Points redemptions or book award nights at any of the 19.2% of the properties that are going up, you should finalize your plans today or be ready to pay (a lot) more starting tomorrow.