I think that Kim has a decent shot at getting a win tonight. The Boston offense is stronger than the Philly offense, and the Philly offense has been slumping badly so there's the real possibility he could get the win over Wolf even if Wolf only allows 2 or 3 runs. It's a decent start, and I'd go for it.
I haven't heard anything committal about what the Red Sox are doing. They still plan to put Fossum back in the rotation from everything I have heard, although they may have him work out of the bullpen for a couple weeks to build up his arm strength instead of sending him on a rehab assignment because they are that desperate for pitching. If the Red Sox get Urbina or Benitez, Kim would stay as a starter, but if they get another starter which is just as likely (Chuck Finley perhaps), they would make Kim the closer.
Even if Kim stays a starter, I think he is a better guy to have on your roster than Dontrelle Willis. People on these boards are overly infatuated with him, but the fact remains that he could start getting hit harder as he goes through lineups for the 2nd and the 3rd time and all rookie pitchers are prone to inconsistency and also wearing down as the season goes on. Kim is on a much better team that will give better run support, and he has the ability to match Willis in K's. If Kim stays a starter, I think he is a top 30 starter.