If you have checked the trailer for the next episode, you can see Jane chasing Red John. Now PAUSE the video at 0:17 (http://www.youtube.com/watch?v=Z77P7ebT0QI). You can see a bit of the hair and now if you compare that hairstyle to any of the suspects..... Its either McAllister or Smith. But by judging the character's height and body shape it has to be McAllister. Just take a look at few pics on Google by searching 'Xander Berkeley' (actor who plays McAllister), and you can see that he has had similiar hairstyles with the same colour matching Red John's hair. 

NB. On Xander Berkeley's wikipedia page, if you check his filmography it says:
- ''The Mentalist (4 episodes, 2008-2013) – Sheriff Thomas McAllister/Red John''.

Regards Dilene!