Here are some of the spoilers that interested me most:

 

"We have no plans for Hightower return but anythings possible."
"New thrills in season four will be about Jane's past. Starting with Ep. 403."
"We have discussed how Jane joined the CBI and there just might be an episode about it in the future."
"Yes, Red John has been visible in prior Episodes. You've got to look for him like Waldo."
"Let's just say Lisbon and Jane have serious issues to work out this season..."

"The most exciting question of the night will be answered in the season premiere. Did Patrick Jane kill Red John?"
"In some future episode we'll learn more about Red Johns techniques i.e what happened to Christina Frye?"
"You will see new and different sides of CHO in season 4. YOU CAN COUNT ON IT!"
"There will be further dramatic complications between Van Pelt and Rigsby's relationship this season"
"We love Currie Graham aka Mashburn and we hope to have him back."