If Brandon Jennings could net Brandon Knight, Khris Middleton, and Slava Kratsov in a sign-and-trade deal this off-season, Lowry should be able to net some decent assets in return.
Tyreke Evans and a 2nd landed Vasquez and 2 2nds.
S&T deals can net some decent assets. Obviously, MU should try to deal Lowry by the deadline, as his value will likely be at its highest at that point. But if there isn't a deal to be had, then keep Lowry and decide in the off-season whether to extend him or explore a S&T deal. If Lowry walks, then the team has cap space. But given the deals MU has made, I think he'll be able to fetch a decent return for Lowry - either at the deadline or through a S&T scenario.