Plec explained that Nina Dobrev's character may reconsider her choice in the season three finale to be with Stefan (Paul Wesley) as she gets to grips with her new form.
Asked if Elena will stand by Stefan next season, Plec told TV Guide: "That's the best question of all. Everything has changed. Not necessarily how she feels about the boys, but who she is.
"This may bring her closer than ever to Stefan, or it may give her a deeper bond with Damon."
Plec also suggested that Elena may even remember that she met and connected with Damon (Ian Somerhalder) before his brother.
"She'll start learning things, like how Damon compelled her to forget their first meeting," the showrunner said. "Those memories will come back, and it'll add more fuel to the fire."
The executive added that Vampire Diaries fans can expect a "very emotional, very complicated first episode" when the show returns.
Dobrev herself has said that she is excited to see what kind of vampire Elena will become.
"Is she going to become a Stefan vampire where she eats bunnies and squirrels?" she asked. "Or is she going to be a Damon vampire where her personality completely changes into a vicious killer?"