On the official starwood/MARRIOTT merger post on Flyertalk, there are a lot of interesting information and accounts of the official ‘starwood Lurker constantly add new tips, answering questions, and be helpful in General. The only thing rumored is the ability to use a free night certificate properties that are more than 35 000 points by paying the difference in points.
Q: if I have a credit card free night certificate and wants to stay in a hotel that requires more than 35K points, I can use my own points to make up the difference? This will be very useful, as there are often no hotels in the area that are available to low number of scores.
Currently no, but we are going to add this feature in the future. <added by starwood Lurker 04Jun2018>
If they add this feature, it will make certificates for a free night is much better, as You are limited in your options. Perhaps they would also add an additional fee for this and to reduce the cost, obviously, but at this stage we can only hope that this will not happen.
Hat tip Chong786