Everything depends on workouts. If Embiid's health issues don't check out, he could drop slightly from the top four. Exum is the most unknown of the four but that could also work to his benefit. The fact that he could play both guard positions may also appeal to teams.
I can see Gordon or Vonleh surprising teams with great workouts and rising a bit, while Smart may drop due to the perception that he's been exposed a little this last season.
Randle is the one I'm most pessimistic about. After reading some anonymous scouting reports on him, it sounds like people feel his ceiling is a little lower than some of the other young PFs in this class (Gordon and Vonleh are two of the youngest freshmen in this class, not turning 19 until Sept/Aug). Randle turned 19 five months ago. Not that I necessarily think that's a huge deal but some teams may feel Gordon and Vonleh have more room to grow.