It would've been better if the reason why Jane joined the FBI is like this: Abbott comes to him, shows pictures of a crime scene: a government official is killed brutally, with a red smiley face on the wall. Jane: "It must be a copycat, I killed Red John." Abbott answers: " We thought so too, until this." and gives Jane a recorded message. "Hello Patrick (saying with the same voice as in season 2 finale and season 4 finale), I hope you've been well these 2 years. You think you killed me in that park, but you were wrong. I'm very much alive. Like I promised you in Lorelei's message, I'm starting killing again. Take care of yourself and Teresa. Bye byeee....." --> Then Jane joins the FBI to catch RJ once and for all... 


What do you think? I hope you liked my suggestion :)