I am sorry to hear of the strained relations between you and your father. Your dad obviously doesn’t want your input, and most likely knows you would disapprove. I would not wait, but rather tell him that you are disappointed in the fact that you feel this woman has eclipsed you in his life. Don’t try to change the wedding, or him, or her. Just let him know your feelings about you.
Rather than condemn her and his behavior, or try to control his decisions, put your emphasis on being honest and telling him how you feel about what has happened. You are the world’s expert on your feelings so you are always on safe ground to express them. As soon as you try to control your father by altering his thinking and behavior, you are in the weakest position with him you can be.
Finally, I would show him this response so that he knows the depth of your concern. From there you can talk about your feelings. Your father is going to be whom he is and will do what he wants to do. The most you can do now is let him know your disappointment and frustration.