It's getting to the point where almost anything in past episodes is now being seen as a 'clue'. Things people didn't notice before, have suddenly become massive clues.
Take the end of this clip for example. Mashburn and Jane walk away, and the camera zooms in on Mashburn's car. The lights and the bumper of the red sports car almost look like a 'Red John' type smiley face.

See how easy it is to make big things out of nothing?

Personally, I believe Bob Kirkland is still alive and his brother Michael was the one who was killed - sacrificed more likely by his stronger brother's alter ego: Red John (Bob Kirkland). Bob probably controlled his twin from the time they were young. The stronger twin usually has some degree of control over the weaker and if Michael 'worshiped' his brother (who happened to be Red John) he would happily die for him.

Some form of mind control/hypnosis will play an essential role in whoever is exposed as red John. (even if not Kirkland)

It's been fun guessing all these years. Going to be sad on some level when it's all over.