This is a young player (28 years young) who rebounded from an awful year to become one of the top 3 point shooters in the league right now (Mike&Tommy seemed to think Lee is 2nd in the NBA right now in 3pt%) and has become a huge spark off the bench for this team. In addition to his shooting, he is also an above average rebounder and defender for a guard. He's got size, strength and athleticism.
Now, I'm not saying that Lee is a starting SG on a championship team. However, do you trade a role player who is thriving in a role that is critical for an NBA team to succeed, who is also locked into a reasonable contract for his role and can still continue to improve?