I think Kirkland suspects Jane of being Red John and that's why he is investigating him , he as an idea that maybe Jane himself is Red John and knows that Jane himself has no idea .

The only way this show can go out with a bang is Jane having a mental disorder that allowed him to have a split personality .

Like it or not anything else would really disappoint me in a big way .

I don't think anyone else as the brain power to outsmart Jane apart from Jane himself .