It's RON. R...ed J...O...h...N.
As Heller said...Red John appeared sometimes, but never obvious. There from the beginning...always able to get all informations. Someone you'll never think off. Take a look at the latest episodes...Ron is there more often than ever. Last Episode Jane asked him:"Did you see Lisbon?"...he answers, walks away fast, while speaking a little like Red John. Even in the new trailer you can see him...

For me it's a teammember in the series from the very beginning and the one which role is written to be the biggest surprise at the end.

ron is red john . Red jOhN = RON
and he is always around and no one notice him and i, the crime scene's 

No explanation required #cbironforlife #hehas69theories #coincidence #idontthinkso #rongetstheladies

I have a very strong feeling that it's CBI Ron. As stated before, Bruno said that RJ is more of a Where's Waldo in the series and that's exactly what Ron has been from the start. He is always popping up, even in the season finale when Patrick killed who he thought was RJ at the time in the mall.

From a writers perspective, why would they have Ron hanging around here and there for 6 seasons? This isn't the type of show that has the same extras just hanging out in the background week after week, so there has to be a reason he is there. Ron just blends into the crowed and nobody suspects him of a thing, even when he seems a bit fishy such as this season already and in the past.

Just my thoughts to add to the conversation.

In the last episode Ron tell Jane that Rigsby is on the phone. So why would Jane sent Rigsby to look for the notes when there wasn't any.
I think phones in CBI are bugged and Jane knows that, so he is giving RJ wrong leads.
An also Ron is RJ or his informer.
Jane is giving a  lot of red herrings now and RJ still thinks he is one step ahead.

Ok this may look strange... but i noticed 2 things in the end of S6 E2 :

1) RJ is talking to patrick on the phone saying  : 

"Can I take a message? ..... .... No ?"
When he says the word "NO" on the phone, HIS BOTH HANDS ARE ON THE KNIFE ....... meaning the actual killer isn't the one talking on the phone...

2) then who's talking on the phone at this very moment ? I just noticed that Ron was going to make a call... and his voice sounds a little like RJ's .... and why would Heller put this "useless" character at such a decisive moment ?

What do you think ?

I think it's CBI RON
I mainly base this accusation according to 2 points:

1-The best way to hide something sometime is to put it in plain sight. so you look over and over around     it but you can't see it because it is not focused on but if you get yourself out of the picture and view it       from other angle you will see it.

2-He is there almost every episode like waldo but you have to look for him and watch his subtle moves     and behavior with other people especially red john disciples.

n.b., the internet sources says he appear on the series starting in episode 17 of second season "the       red box" and this is wrong, they started credit him since this episode but he was first seen in episode 7   of the first season "SEEING RED" and many following episodes but was not credited.