TV Guide has the major scoop on the character that will leave Mystic Falls:
I can’t wait for The Vampire Diaries to return! What can you spoil? — Heather
NATALIE: When Klaus decides to take up residence in Mystic Falls, Elena will learn the hard way just how much danger she’s putting her brother in. “There has to be a big change,” executive producer Julie Plec tells us. “What that is, and what she does, is part of the first episode back.” Let’s just say we might not see Jeremy for a while.