Executive producer Julie Plec has revealed some tidbits about season 4 of The Vampire Diaries, which premieres in October 2012:

– Elena will indeed complete her transition and become a vampire
– Elena’s transformation will affect her feelings for Damon and Stefan
– The central love triangle is far from over
– When Elena becomes a vampire, her highlighted trait will be her compassion
– Joseph Morgan will return as Klaus
– The fact that Klaus is possessing Tyler’s body won’t be a secret for very long
– Matt will seek retribution for what happened to Elena by going after Rebekah
– The Matt/Caroline relationship might be revisited
– Caroline will begin to develop into Stefan’s “new Lexi”
– Bonnie’s dad will finally be introduced
– Damon will continue to evolve
– The characters will graduate high school

We’ll add more as new information is revealed!