A little more info about The Mentalist finale from Ashley Gable via TVGuide:
So excited for a two-hour Mentalist finale! Tell me about Red John!
ADAM: Executive producer Ashley Gable, who wrote the first hour of the finale, shares your excitement. "This changes everything," she says. "There is a confrontation between Jane and Red John like we've never seen before."
Translation: Jane and his nemesis will finally come face-to-face after Red John's mole in the CBI is revealed. So will the audience also see him? "There will be no scary masks in this episode," Gable teases.