I still think that its him. RJ has to be a charismatic person and none of the main suspects is. He is very intelligent, convincing and charming and when he is around PJ he ACTS as a very friendly person, letting him drive his car, having fun, laughing a lot, acting as if he was a child sometimes etc. Like saying: Ey Im just an extravagant millionaire dont take my serious. 

RJ followers would die for RJ and i dont imagine anyone dying for bertrand or haffner but i could imagine people following WM. He is also the character that looks like more harmless and it would fit in a "shocking" ending. Also I think he had sex with Lisbon for a reason. Like it was part of some kind of plan or message. After that he didnt appear again and I think that  its something that was written for some reason and it could be explained later.

Also Lisbon has been acting suspicius during this chapters and I think that they want us to believe that she is part of the bad guys but in the end I imagine that she would be non guilty.

I also dont know what the planning for the tv show ending. It looks like they are following the 7 list of suspects and the last man standing has to be RJ. I hope that that wont be the ending but it could be just like that. I would like something more tricky but last 5 seasons didnt have many complicated stuff. There are so many clues in the air and I think that the finale wont explain everything.  think that the ending may suck a little bit because he have so much espectations . conspiratory theorys trying to explain every act, every suspicious look... Im pretty sure that it would end in an easier way. 

Look the examples of Prison Break or LOST. So many stuff in the air and in the end....  They want us to watch the next episode so they make us believe that the final is going to be great and that all the 500 clues are going to be explained and its not like that. The ending is just an episode, what cares is the previous 20.

Continuing with the WM theory, If you were RJ why would you live hidding from everybody or having a regular job like the sheriff or partridge or haffner... You should act as if you had nothing to hide like Mashburn does but also not letting anybody be too close to you.

Mashburn is RJ!!! Who is with me?