Going to be hard to keep him and Kemba, especially since Marcus is probably due a pay raise. Even if it is just for one season (22-23), that season will be laughably bad as far as the tax goes w/ Rob's contract also coming up.
If we are able to trade Smart for good value (mid-low lottery pick, exciting player on rookie contract), then by all means, we should look to do that. But if we are going to trade him for the equivalent of Mo Wagner/Luke Kornet and not get any picks back, then we should just ride with Marcus until he expires. A guy like him always give you a 'chance' if you are healthy and jelling going into the playoffs.