I think its pretty simple:
If he is a projected lottery, he's gone.
If he is first round but out of the lottery, there is a good or even likely chance he's gone.
If he drops to 2nd round, he'll stay.
What's not simple is where he ends up. Some have him projected lottery still based on reputation and potential since he hasn't shown or not shown anything to refute that. Now that he's playing regularly, he will start to be compared directly to the other draftees. If he out performs most of them, he'll go lottery. If not, it will depend on what he hears from teams that may want to take him and where. If he doesn't get a strong indication that he will be taken first round and/or to a team that is a good situation, I think it would be just as likely that he returns.
I think what we are all really arguing is whether he will perform well enough and better than other draftees to keep his presumed lottery position.
I personally don't think lottery will be guaranteed for him by the end of the season, but will be on the cusp and will likely go first round shortly after lottery, and unless it looks like a bad situation shaping up and he widthdraws, I think he ultimately will go pro. But of course, that's just a guess and gut feeling, and anyone that claims more certainty what will happen really doesn't know either.