I think Duclair gets 9 games and heads to juniors unless he is near spectacular.
That's what i think. Especially since Stepan will return soon thereafter. It makes sense forward-wise on the roster. Duclair can get his earned cup of tea, Stepan rejoins the team after 7-12 games - probably right around 9 to 11 when Duclair gets sent back. Then they can shuffle the wingers around and get St. Louis back where he should be. Then Duclair can go back to the Q, dominate and get his Memorial Cup.
The wildcard here is what happens if Duclair continues to finish like he did in the preseason and youre instantly looking at a Calder candidate with 4 goals, 3 assists in his first 8 games? Tough decision then. If he proves he can play in the regular season it might not be the best for his development to go back to a lower level.
Rangers management would know best imo. I think they know what they want to do already. 82 games + playoffs, traveling all around, against men (some twice his age) is a long, grueling season for a 19 year old forward.