Well, by the looks of it http://www.breathecast.com/articles/the-mentalist-season-7-release-date-plot-spoilers-new-season-pat....
the romance is what we are going to see next season, and a trouble in love triangle. Unless Agent Marcus is Red John (He is MAR...) I don't think Red John will return.
I wonder if Jane's hesitation to reveal his feeling to Lisbone was in fact his knowledge that Marcus is the Red John and not his love to her. By confessing he tried to keep her away from Red John.