Who will win Iowa? My guess is Gingrich, but we've got a long time until January 3rd. Nate Silver, whose work I admire, has this current finish predicted for Iowa, while political odds makers still favor Romney to eventually win the nomination.
I agree with Ed that Ron Paul will do well in Iowa and New Hampshire. My own sense is that his success simply serves as a shield for Romney and Gingrich, since it denies any possible oxygen for the second-tier candidates, and Paul will never actually win.
One final point: I'm not sure Iowa, in this cycle, is still the state where organization trumps everything. I think that's true for Paul whose supporters have been personally committed to his libertarian purity for many years, and are not influenced by the current fretting among Republicans. But most caucus-goers in Iowa are organized around this fervent desire: who is the most truly conservative candidate who has the best chance to beat Barack Obama. Their two main choices are still Romney and Gingrich, and according to the NBC-Wall Street Journal poll they are not very excited about either.