Jinn will replace Jacob by Gareth

Ok...

This assumes Jacob is a 'good' guy and is based upon his conversation to Richard on the beach in Ab Aeterno.

The default opinion is that Jack will replace Jacob because he is the 'main' character. I think Jack's main role will be to try to stop MIB leaving the island on behalf of Jacob, but not to continue Jacobs work. The problem is, Jack has been corrupted by the island and is guilty of murder. He wanted to 'blow [the others] to hell' and got Sayid, Bernard and Jinn to carry it out. He pulled the trigger of a loaded gun on Locke (despite the gun not going off, Jacks intention was to kill him). He also randomly fired his gun at the people of Dharmaville, killing 3, then another at the site of the 'Incident'. And he tried to detonate a hydrogen bomb! Jack is a murderer.

Everyone considers Hurley to be the 'good guy' and he is the only one who can communicate with Jacob, but he is just being used to move pieces around the board of whatever game Jacob is playing. He seems harmless, but he did mow down an other on the beach in his blue Dharma van. So Hurley is a murderer.

Sawyer - I don't need to explain how many people Sawyer has killed, both on and off the island. A murderer.

Kate - Same for her, a murderess.

Sayid - Um...Murderer.

Sun - She shot Colleen, a murderess.

Jin - He didn't kill anyone! He couldn't bring himself to kill Jae, he just gave him a beating. At the ambush on the beach at the end of Season 3, he missed the explosives, thus not killing anyone. In fact, Jin has grown in virtue more than any other character on the show. He tried to save Justin's life when Claire had them captured. He is the only candidate who hasn't murdered anyone, in fact. Right from the start, Jin has been of service to the other Losties, fishing in season one and offering them food, helping them to live.

Jin has been the most helpful character in the show, always of service.

So assuming the idea of candidates comes to anything, Jin is the favourite.

The rest of them are killers, not good people.