First, let me calm everyone down: Caleb Swanigan is coming back for the 2016-17 season. Yes, he has declared for the draft, but under the new rules a lot of players are going to declare, go through the evaluation process, and eventually return. It would not surprise me if Vince Edwards and Isaac Haas did the same before too long. If you have any chance at the NBA a player is going to do it, get evaluated, learned what they need to work on, then return.
Swanigan is going to return because, while good, he is no ready.