I feel like, for the second season of Vampire Diaries, we need to have an "In Memoriam" segment. An awful lot of recurring characters died: Mason (heart ripped out by Damon); Rose (werewolf bite); Luka (charred) and his dad (bitten by Katherine and finished off by Stefan); Isobel (self-immolation); Jules (heart ripped from her chest); Jenna (sacrificial lamb); John (self-sacrificing lamb). This, of course, is not counting the people who died then came back in one form or another (Caroline, Bonnie, Elena, Jeremy, and Elijah, plus first-season casualties Anna and Vicky).
So what do you think we will face in season three? It seems that the Salvatores are being set up to switch places. Stefan is going to go on a cross-country killing spree with Klaus, while Damon stays behind to protect Elena - and try to get into her pants. I suspect he will be successful. But remember, at the beginning of the season, Stefan was building his tolerance towards human blood. I don't know if it will combat the dozen or so bags of blood - and the innocent girl - that Stefan drank down in the season finale.
Meanwhile, Damon and Elena - and whoever else makes it to season three - will revive Elijah again and he will help track down Klaus. I suspect Elijah will revive his family to aid in the hunt. Some may defect to Klaus's side, or he will find some of his original werewolf half-siblings. Either way, it will be the war of the originals.
Jeremy's story could go in a couple different directions along essentially the same story arc. He may have "the sight," or some spirits tagged along from the other side. I assume that Jenna will join Anna and Vicky in haunting him. It's going to be bad - I think whatever happens with Jeremy will be the consequences that the witches warned Bonnie of. Bonnie will still have her powers, but the witches won't back her up anymore. Since The Secret Circle seems likely to get a series order, I suspect Vampire Diaries will tone down the witchcraft.
And finally, I think that Alaric, after seeing Bonnie get Jeremy back, is going to try to bring back Jenna. If he succeeds - and doesn't destroy himself in the process - Jenna is going to come back evil.