If he is not traded, or if he is signed before free agency, Lee's worth will be determined by what another team is willing to pay him. The Knicks can match or not match. If they do not match, the Knicks get nothing in return.
I expect that Lee might be willing to take a New York discount. If the Knicks want him, they should try to sign him and avoid matching some other team's offer. If Curry and/or Jefferies can get off the books before 2010, the Knicks are likely to sign Lee.
Although other teams value Lee highly, I am not sure he is easily tradeable. He will not have to sign with the acquiring team because he is on the road to free agency. I agree with abcd that Lee's trade value is currently high. Walsh has a problem. It can be fixed if someone will take Curry off our hands, but that is not going to happen before the trade deadline, because he is injured and totally out of shape.