Under normal circumstances in a business outside of baseball, Theo would remain under contract with the Red Sox for 2012 and the Cubbies would have to have Hoyer or someone else run the team during 2012. They couldn't contact Theo, because that would constitute tampering. That would be an ugly situation for all so Selig would no doubt exercise his czar-like powers and step in for the "good of the game." The Cubs know this, so the Sox have no leverage. The Sox are going to end up taking whatever Selig decides they should get.
For people as old as me, they might remember that Dick Williams quit on the A's after the 1973 World Series and signed to work for the Yankees in 1974. Williams was still under contract with the A's for at least 1974. Charlie Finley would not release Williams from his contract, so the Yankees had to hire a new manager, and Williams was without a job for 1974, because he refused to work for Charlie Finley. Finley gave Williams permission to manage the Angels in mid-1974. They were a terrible team.