Starwood just released a list of their properties moving up (218) and moving down (48) on March 5, 2013, in award categories. You can book using the current rates until March 4 as far as the hotel has loaded award availability.
Note that SPG can make more changes to award categories before the change takes effect on March 5. Last year, there were quite a few properties that did change in fact. You can access the PDF file here.