I really don´t want to offend anyone but I find very unlikely that Michael Kirkland is Red John or will be performing in next episodes of the mentalist. Introducing his character is an explanation why was Kirkland chasing Red John for himself and it also explaines why he asked people do they recognize him(to see if they knew his brother and could provide him with some information). Kirkland is dead,also is Partridge and that is it...introducing a new character in 6. season who is possibly Red John would just seem like amateur writting,also Bob stated that his brother was approached by Red John excluding Michael from being Red John himself.

It was just Heller´s way of explaining Bob Kirkland story,there is no extra meaning or something hidden in that. Michael went missing(is probably dead),Kirkland is shot by Reede Smith,that is it. We won´t see Kevin Corrigan anymore in this show.