It's hard to choose because I don't really want any of the main characters to die, but I know that some of them will by the end of it all. I can see a lot of sacrificing themselves for each other between Elena, Stefan, Damon, and also Katherine happening in the long run. And also, Tyler and Caroline and Matt and Caroline.
I honestly think Elena will die at some point. I wouldn't be sad if she was gone forever, but the show is basically all about her so... It just would not be the same.
I would be really sad if Stefan or Damon died, but I am sure one of them will eventually. Also, Jenna, Jeremy, or Alaric. That whole group has gone through enough. Leave them alone. And if Caroline died I would probably scream bloody murder. Also Matt... I just him and Caroline ending up together in the long run.
Katherine is fierce and I love how powerful she is. So obviously I want her around.