In season 2, the Stefan/Elena/Damon will evolve into a Stefan/Katherine/Elena/Damon quadrangle and surprisingly it will be Stefan, NOT Damon, who will be the most affected by Katherine’s return: it will turn out he’s not as over her as he thought he was. Elena will come to come to terms with the fact that she may have developped feelings that are more than friendly towards Damon. Damon, on the other hand, will be busy devising a plan with the Council of the Founding Fathers to take down Katherine.
And yes, werewolves will be introduced next season and one of them (probably Tyler?) will connect with a certain witch (Bonnie?) while trying to deal with how to cope with their supernatural abilities.
Now 4 the next one, Next season, the appearance of the villainous Katherine in Mystic Falls throws a wrench into the love triangle between Stefan, Elena and Damon, and the other residents of Mystic Falls must choose sides as they fall victim to a new breed of danger. New and unexpected friendships will be forged, allies will become enemies, and hearts will be broken. Stefan and Damon will be forced to face a villain more evil and diabolical than they ever believed possible. And they’ll take their shirts off. Frequently.