Red John will eventually be caught and we'll eventually be able to see his face. The questions is whether we've already seen him. There's been theories thrown around, so I'll throw my hat into the ring. Minelli is Red John. I know that's been said many times, so here's my reasoning based solely on last night's episode.
I found a striking parallel between Minelli and Red John. Red John had screwed up, possibly leaving DNA evidence. He saved himself in essence by cutting off his right hand (Rebecca). He threw her to the wolves with no intention of saving her.
Minelli on the other hand quit, because he hadn't lost any agents in 8 years until now. He finally had enough and could retire without any more pain.
But what if quitting was just a smokescreen for his inadequacies as Red John. He saw how close he was to being caught and now wants out. Red John may not have a pathological need for murder which is why he is able to leave everything behind.
You might ask why Rebecca told Jane that Red John killed Bosco and his team, because Jane wanted it. Going along with the rest of my theory, if Red John was quitting, the implication that Jane killed Bosco could be his last attack against Jane. We see how Jane reacts afterward. He's just sitting there silent; her words had a profound effect on him, and if it really was Red John's last attack, it was effective.
I remember Bruno Heller saying something along the lines that Red John may never be caught. I don't like this idea at all, and would like to see further progress in the Red John story. It is the one thing compelling Jane, but at the same time, he has to get on with his life.