If you look at The Mentalist Wiki website there is a list of upcoming episodes.  The episode before the "Red John" episode is entitled "The Great Red Dragon".  I realy think that all of our theories will be answered on that show.  I think the seven suspects are akin to the seven headed dragon painted in a series of paintings by William Blake (author of "The Tyger") poem.  These supposedly represent the devil ( the 666 reference in the hallway in 6x1) and I think that it will be shown that all seven suspects were in a conspiracy of some sort that invloved the seven-headed evil dragon. 

The "Red John" episode will focus only on the clues to the Red John story that we have all debated endlessly about for the past few years.  The focus will be on Kristina Frye, Rosiland Harker and maybe even Erica Flynn.  There will be some resolution to the Red John story (Patrick will have to win)

The next episode is supposedly "My Blue Heaven" which will be the first part of the next Mentalist chapter with the new characters introduced in the CBI and Jane's life will be a lot happier.