It's Ray Haffner. It makes complete sense. I mean, think about it. Red John killed somebody at a farm operated by visualise. That was probably his first murder, and he was probably 20. It's been 30 years since that roughly, and Patrick Jane has shaken hands with Haffner. Haffner is a member of visualize, and makes complete sense. He denied the topic when Lisbon brought it up. He pretends to be awkward, but we all know he really isn't. 
There is little doubt in my mind he is Red John.