Smart is what he is, he'll improve a bit as years go by, but he'll always be a "Junk Yard Dog" that needs to improve his scoring. His value is, he defends 3 positions well, he's the intangibles master, and he's hard nosed. He is the "Junk Yard Dog"
On the flip side of the coin, Marcus will never be that player who asks for a Max deal either, or more money than what he's worth, IMO he'll play his heart out for average NBA money, he'll always be a great addition to a contender.
You either value a player like that, or you don't.