I hate to be a buzzkill, no one is hoping for the return of Red John more than yours truly. However, this imdb post: http://www.imdb.com/title/tt3275764/?ref_=tt_ep_nx has been getting a lot of attention and I hate to see people get their hopes so high. I recently posted this in a comment on a theory, but I am posting this here to get more visibility.

As much as I am dying for this to be true, it's almost certainly not.
Particularly telling is the fact this description conflicts with the
CBS press release and additionally, whoever wrote this summary was not a
professional writer -- most likely some random internet user.

The
reason I know this is the tense-switch mid sentence, if written
correctly it should be "After Jane finally comes to terms with his past,
his nemesis strikes once again, committing murders at different
locations seemingly at the exact same time". Notice the use of "comes"
instead of "came" early in the sentence. Additionally "committing" and
"different" are both misspelled. A professionally written episode
summary would not make such mistakes, and as such, as much as it breaks
my heart: this is fake.