The last name called is typically reserved for the captain of the team, but since he was shipped off to the Dallas Mavericks earlier this season, Boston had to make some adjustments. It's nice to see that the team is committed to Smart and view him as a leader and worthy of getting the last call. That said, it's not exactly a ringing endorsement when two players have to be traded away and another one lost for the year in order for Smart to get that recognition.
He is a rookie, though, so it can only help his confidence to see the team trusting in him. It'll be interesting to see what happens when Sullinger returns healthy, but who knows what the roster will look like by then or if he'll even be on it. This summer should be nuts.
As for who else could have that spot, Brandon Bass or Avery Bradley could make a case due to their long tenures with the team. But Bass may not even be around next season, despite what Danny Ainge says now, and Bradley seems more content to play a complementary role instead of trying to be the face of the franchise. Neither Tyler Zeller nor Evan Turner have any real claim for that spot.