They'll probably keep Justin around for a while. He's the villain this season. They need him for the "Oh no he di'nt" factor.
LeShawna, Harold, Heather, Beth, Lindsay. Some permutation of that series is my guess for the next 5 bump offs. Like people said, LeShawna's worn out her plot. Harold will leave as soon as the sendup to "Seven Samurai" is over. Heather will get kicked because she reverts to her bichy self some episode. Lindsay and Beth are gone because one's an idiot who doesn't help the team, the other's not that well liked (There are ZERO beth fanboys on the Internet. If you can bring me proof of one, you can have 700 billion in bailout money.) But Gwen is probably next on the chopping block because she allegedly "rigged the vote". She may have influenced the vote, but she's no Karl Rove.