The proposed rate is roughly 2.5% on average by class. The First Class stamp will go for .50 to .55. This is the largest price increase since the introduction of the Forever stamp.
If you are budgeting for your direct mail in 2019 you might want to keep in mind the 2.5% increase.
If you are using first class stamps for personal or business purposes, I suggest that you stock up on Forever Stamps before the November 27th increase.