Honestly, this should be expected due to the injuries he's dealt with and being played out of his natural position/role.
So it will all depend upon how he's utilized next year, which obviously depends upon this summer goes. If it goes well, we don't resign Turner, and Smart ultimately becomes the primary ball-handler/scorer/guard for the bench, then, yes, I expect a sizable leap from him, even if it's just skills-wise and with the eye test rather than major leaps statistically. On the other hand, if we keep playing him as a spot-up shooter, then I expect much of the same - lackluster offense and elite defense.
We honestly should be putting a lot of time and energy into developing Marcus, because it could ultimately work out really well for us contractually. Think about it - IT becomes a free agent the same summer that Smart is a restricted free agent. If we properly develop him in a Livingston/Golden State type role off the bench, then we can ultimately pay Smart what he'll demand as a free agent for him to take over the point guard role full-time that summer.
The prevailing opinion on here is that we're not going to want to pay IT the major upgrade in salary that he's going to demand that summer, especially due to his size and the history of smaller guards like that not lasting too long in prime condition. Thus, if we ultimately develop Smart into our starting point guard and tell IT that we'd love him back that summer, only in the sixth man role, then he can either sign a big contract elsewhere or take the hometown discount for the only team in the league that has believed in him and allowed him to shine.