The title is a bit misleading. He is not entering the draft, he's testing the waters without signing with an agent, which the new rules allow. He can play in the combines, talk to team representatives, etc. If he doesn't like where teams anticipate him being slotted (i.e. anywhere outside of the 1st round), then he can come back to school.
On the one hand, he's not NBA-ready by any stretch....his handles are below-average, at best and he's not particularly quick. On the other hand, given the vast inexperience coming back next year, his stock likely won't be any higher than it is this year. It'll be interesting to see how this all plays out.
From where I stand, there's very little chance we make the NCAA's next year....even with Jok coming back.....so if he leaves, it's not like it's going to cost us a bid. And with the logjam at the 2/3 spots, it'll be good to get the young guys out there sooner, rather than later....they'll be better for it in the long run or it'll become apparent pretty quickly that they aren't B1G material.