To add to what I posted earlier...

What do you think of this idea?

Maybe Red John could have been some sort of cult. A sort of guru- disciple thing- with only one disciple at a time.

So the red barn could have been done by the 'previous' Red John. Jane's family would be killed by 'current' Red John. And at the end when Jane is killing Red John- the serial killer tells him in a mocking way- 'but I am already succeeded' or 'I have already been succeeded'...and so Jane is faced with a dilemma- should he kill the guy or should he keep him alive to find out the identity of the 'new' Red John?

Sorry about my english.