Exactly. The only chance of a Kerry-like defeat of Huckabee is if Fred Thompson somehow makes a move in Iowa. That is going to be tough since Huckabee seems to have the Christian vote locked up.
Remember that Iowa is not a primary state. It doesn't matter what the polls say. It's who can get their supporters to the caucuses at the time and place appointed.
Also keep in mind that no republican delegates are actually elected at the caucuses. We take a straw poll and we elect delegates to the county conventions, which then elect delegates to the state convention, which then elects delegates to the national convention. We won't know who really wins Iowa on the republican side for a number of weeks, yet.
Since the caucuses are about orgnaization, I wouldn't rule Romney out just yet (even though I won't be voting for him).