He will be revealed as Red John. He might not fit the exact description of Rosalind Harker. That is the point, how can a blind woman tell the height of someone. Look at Bertram, he might have worn a wig to pretend he was someone else. He sounds creepy at times and he walked out from the mall in Season 3, because he knew Jane would find out the fake Red John. His hands and Haffner's hands are the ones that match Roy's when he visits her. One more interesting fact is that the actor who portrayed RJ when he visits Harker was none other than Jane.
How do you find this theory?
plausible
unlikely