I was just thinking about the possibility of Red John's return;
One part of my belief that Red John will return was the titles of the episodes:
for all five forst seasons, most of the titles of the episode had "red" in their names, or a reference to the color (blood, strawberry, cherry, blush for example).
As i'm french and i used to be looking to the episodes in french with a translation that did not include those references most of the time I did not pay attention to this before.
If you want to check, here is the list of the titles of the episodes from s1.
Since the "end" of red john, whiwh is supposed to be a fresh start for jane yet the titles of the episodes have kept references to colors in their names, every color except the red one, of course :
9-My Blue Heaven
10- Green Thumb
11- White Lines
12- The Golden Hammer
15-White as the Driven Snow
17-Silver Wings of Time
19-Brown Eyed Girls
20- Il Tavolo Bianco (the white table)
I don't really know how to understand this but it can't be a coincidence or routine. We are all expecting the red name to appear in the last episode aren't we ?