IMO three tiers, within which I don't really have any basis for deciding.
Tier 1: Aronian, So, Liren
Tier 2: Kramnik, Caruana, Karjakin
Tier 3: Grischuk, Mamedyarov
I think most likely is Aronian, for experience, consistency, and his recent superb form, or maybe Liren as I think he's a generally underrated player, and I'd be psyched to see either to be honest. So I'm not as confident about, but I wouldn't be surprised to see him finish top given his attacking style which could take him to an early lead.
Caruana is one of the stronger contenders, but he doesn't seem to play as aggressively, which I think will hurt him. Kramnik I think is in the mix, but both older and less immediately impressive, and given Karjakin's performance in the Championships was a stale drawish sandwich, I don't think he'll do great.
Grischuk and Mamedyarov IMO aren't as consistent or, to be frank, as good as the others.