The rumor I keep seeing is that there's an issue with a shoulder, but I don't see a scenario where you would take him. The top tier of the draft next year is stronger than this year's was, so I think that alone would eliminate the possibility. It's hard to say for sure, since a healthy Rocker is probably somewhere in the top half of the first round mix, but I don't think anyone is is going to take him over premium college bats or a even the prep guys. One way to look at it is that the Mets have already signaled they'd take pick 11 in next year's draft ahead of him, so it'd be surprising if he went before that pick.
Blind guess, but he seems like someone who would get picked once it moves into the consensus second tier of the draft and a team's turn comes up who lacks a consensus top guy on their board. I don't think anyone is going to take him extremely high, but once it gets into the second tier where more preferences come in, someone could still grab him. The obvious caveat is that it's a pretty unprecedented situation and in theory you can have pitch data/showcases which could calm any worries.