He's a useful player to have at the end of the bench in the regular season. Someone who can change the tempo and complexity of the game entirely by using his speed and on-ball harassment.
However come playoff time, he's pretty close to unplayable when it matters most because of his defensive liabilities. In the modern switch-happy league, teams will simply force a switch and have Larkin try to guard somebody much bigger - LeBron, Durant, Harden, etc. It was tough enough trying to watch Olynyk and Rozier try to contain LeBron over the past few seasons. Larkin's lack of size would put a lot of pressure on our defense.
So I guess we'll see. I appreciate his contributions this season and wouldn't mind having him back for the minimum depending on how the rest of our roster looks, but won't be too upset if he doesn't come back.