Interview excerpts lifted from ET online with smart-ass remarks from yours truly
Heller: It was very much designed as an encore, a curtain call for the show and the audience. You don’t come out for the encore and do death metal or dark stuff.
Quitthat: Unless you are Cannibal Corpse. Can you imagine the look on the faces of their fans at the concert hearing the band play "Chitty-Chitty-Bang-Bang" or "Sound Of Music" with accordions and fully dressed like polka yodelers? Mentalist was dark, should have ended dark, in order to stay true to itself.

Tunney: Fans of TV shows are so committed to the characters and to the story. When you do something that’s drastic like this, bringing two characters together after six years of knowing them platonically, they can turn on you really easily.
Quitthat: You don't say!?

Tunney: It’s our best version of a romantic comedy with some crime thrown in. 
It’s for the fans. 
Quitthat: Why do I feel the sudden urge to quote Lloyd Christmas? "Auffiderschnitzel"

Tunney: There’s nothing more frustrating than being committed to something for seven years and they don’t give you definitive endings.
Quitthat: Ditto. Are you sure, you're not psychic?

ETO: Do you foresee 10 years down the line, a Mentalist 2.0?
Heller: Absolutely, it’s a date. We’ll all be there in 10 years. 
Quitthat: Dream on, buddy. As the saying goes; it's not done till the fat lady sings. 
Here is the 2.0 version of the saying; Once the boss, kick-ass strong female character is reduced to a housewife, you know it's done... like the bun in the oven.

Thank You WHO IS RED JOHN? It's was great pleasure reading and sharing theories here with intelligent and creative, like-minded, true fans of the show, like yourself. 

P.S. Mr. Heller I'm keeping my Brett Partridge vote as a small token of middle finger to you. I hope you don't mind it.