it's not doubtful at all. Pettersson has the highest ceiling of a non #1 draft pick in recent memory. His IQ/Passing/Puck handing is elite. His shot is near elite. His skating/speed is excellent. His defensive play is excellent. He has NO weaknesses in his game, skill wise.
Literally the only thing ANYONE can complain about him (if you read Pettersson thread) is that he's too light/weak. You can't say anything about his actual hockey skills. Because of that, his ceiling is MASSIVE. He's the most skilled prospect right now. Will those skills translate to NHL? That you can argue about, but not about his ceiling.