I think Kotkaniemi will be an elite set up man who can score goals if he sees an opening. He’s gonna have to play with 2 snipers to be at his best and reach PPG+
Most elite players play in the NHL at 20 and are able to be productive. Let's look at the top 20 scorers at 20 years old.
Draistl : In the NHL 51 points.
Pasternak : In the NHL 70 points.
McJesus : In the NHL 108 points
MacKinnon : In the NHL 52 points.
Panarin : In the KHL 31 points in 50 games (which is not bad for a 20 years old he was traded toward the end of the season and was still the 2nd scorer of his first team at the end of the season).
Eichel : In the NHL 57 points
Marchand : Not in the NHL one of the few elite late bloomer exceptions but there's an exception to all rule.
Kucherov : In the NHL 18 points in 52 games (not a great season but still played in the NHL and did 65 points the next season as a 21 years old)
Kane : In the NHL 70 points
Matthews : In the NHL 63 points
Huberdeau : In the NHL 28 points in 69 games (did 54 points the next season as a 21 years old)
Carlson : In the NHL 37 points (he's a dman for god sake and still did 37 points as a 20 years old)
Stamkos : In the NHL 91 points
Connor : Not in the NHL (did 57 points the season after as a 21 years old).
Scheifele : In the NHL 34 points in 63 games (did 49 points the season after as a 21 years old)
Marner : In the NHL 69 points
Malkin : In the NHL 85 points
Ovechkin : In the NHL 106 points
Pettersson : In the NHL 66 points
JT Miller : Not in the NHL (not really an elite player either in my book probably a career year)
So out of the top 20 scorers in the NHL right now 12 players were in the NHL at 20 and did over 50 points so 60% of them. One of the 8 players who did not meet that target is a dman and he did 36 points which is very good for a dman at that age and i would say an equivalent to 50 points. So i would lean toward saying 13 instead of 12.
Only 4 players were not in the NHL (played under 40 games) at 20 years old and one of them (Miller) is not what i would consider an elite player he's having a career year and another one was in the KHL which is a better league than the AHL in my book. I would not call not playing in the NHL at 20 years old for an elite player an exception but it's definitely not the rule. Also most of the players who did not meet the 50 points target as 20 years old did it the next season as 21 years old so not doing 50 points as a 21 years old for an elite player definitely lean toward being an exception.
It's not past midnight for JK but it's definitely slowly getting there if he can't play in the NHL next season and be somewhat productive. If he spend a full year in the AHL next season he'll already be out of the norm. If he doesn't do 50 points the season after as a 21 years old after spending a full year in the AHL then it will not look good at all as he'll fall in the exception territory and no team should bet on an exception to happen.