Bruno Heller said we'd all be disappointed when we find out who's Red John, well i'd be very disappointed if it is Ron from CBI, but it also makes sense. 

We've seen him since the first seasons in short cuts;

Patrick says  "Hi Ron" in an early episode of the season, that made me suspicious, like he knows but he wants us and Ron to think that the man is on the list.

Plus another greeting, in the last episode 6x07, this time is Ron who says "Hello, boss" to Bertram who just got out of the hospital. Just little hints, like later when the FBI shot down CBI we can see Ron is in the scene.

I think Ron aka RJ put the bomb in the house, plus Jane knows or at least suspects him.

(It can also be that Ron is Kirkland's twin, but i find it unlikely.)