Hi everyone, 
In response to the theory below me, on the point of why Rigsby and Van Pelt will come in the final episode.......................... it's pretty obvious that they are invited to Jane and Lisbon's wedding         (*tries to not choke with disgust while typing*).  The name of the last episode is "White Tulips" , put two and two together and it's obviously a setting for a finale wedding. And Rigsby doesn't have what it takes to pull off what Red John did anyway, so your theory is wrong nonetheless.