So Red John is middle aged
So we can rule Stiles out and McAllister as i cant see any body calling McAllister middle aged 
(https://twitter.com/mentalistwriter/status/114530384280158208)  on the 16th of september 2011 the writers said that Red John has been visable in prior episodes and season 4 hadnt started by then so that eliminated Smith Kirkland (who i belive will die in nxt episode anyway) and Halfner (:( )
leaving us with 2 suspects Bertram and Partridge of cause Partridge is dead but there is that possibility he could be alive you never know what Brunno has up his sleve

so that would make Red John Bertram now I was pretty dissapointed when i figured this out I really thought it could have been Halfner so what i think has happened is Halfner and/or mayby Smith and Kirkland have appeared in the background of preveous episodes as the writers said you have to look for him like waldo

What do you guys think :)