Now let me state my personal perception of what will happen in the finals.
First of all, I don't think Anderson would be affected too much by the lengthy match. It was not grueling and mostly serve fest.
As all of us feel, Novak's return was terrible in the SF and also he was mostly pushing the ball and never looked dominant, even though he won. If that Novak shows up, Anderson has a chance to win. It is because he has a good serve and weak returns would not do the job. Also, Anderson has decent baseline play to hang in with Novak, in case the point does not end by means of an Ace, Unreturned Serve, or 1-2 Punch.
Having said that, there is a reason why Novak was so tentative. He was not sure whether he had come back fully or not. He was not sure whether he can really win against Rafa. However, now that he has won, his confidence would be skyrocketing and his old game (i.e., good returning, DTL shots on both forehand and backhand side, no pushing) would come back to him. Even if it does not come back all the way, it will come back to the extent needed to win against KA fairly easily. You cannot underestimate what confidence (gained by beating a fellow member of big three in a GS at business end) can do to a man.
So, I go with Novak winning the match in 4 sets.