To me it seems like the NBA selects players based on potential. Caleb Lohner clearly has NBA potential. The form on his shot is perfect. He is fast enough to switch onto guards and big and strong enough to guard 4s and 5s. He was a guard in high school so he's a pretty decent ball handler. He can jump out of the gym. And he's a willing defender and rebounder.
If he can slow himself down a bit at times (Wooden said to be quick, but don't hurry), learn to be crafty in how he plays, and keep working hard he has a shot at not just making the league but being an upper tier player.
I don't understand why people would want to pump the brakes on this. While it's true that he isn't yet ready, most players who get drafted aren't ready either and few of them have Lohner's long term potential. Nowadays, if someone doesn't come out by their sophomore year they likely aren't going to get drafted. I hope he takes the next step and leaves next year. That would do wonders for BYU's recruiting.