I think it's fair to expect to draft a top line forward if you draft a forward in the top three picks of a draft. Forwards taken in the top 3 picks since 2013 and the number of seasons it took to reach 0.78 points/game (top 96 scoring forwards in the league scored at least 0.78 points/game this season) in a season:
2013: Nathan MacKinnon D+5, Aleksander Barkov D+3, Jonathan Drouin D+NOTYET (now D+10)
2014: Sam Reinhart D+8, Leon Draisaitl D+3
2015: Connor McDavid D+1, Jack Eichel D+2, Dylan Strome D+8
2016: Auston Mathews D+1, Patrik Laine D+1, Pierre-Luc Dubois D+NOTYET (now D+7)
2017: Nico Hischier D+5, Nolan Patrick D+NOTYET (now D+6)
2018: Andrei Svechnikov D+2, Jasper Kotkaniemi D+NOTYET (now D+5)
2019: Jack Hughes D+3, Kaapo Kakko D+NOTYET, Kirby Dach D+NOTYET (both now D+4)
2020: Alex Lafreniere D+NOTYET, Quinton Byfield D+NOTYET (both now D+3), Tim Stutzle D+3
Barkov, Draisaitl, Hughes, and Stutzle took until their 3rd year. McKinnon and Hischier took until their fifth year to break through into bona fide top six forwards. Lesson here is, be patient.
One could argue given injury and illness that Byfield really just finished his D+2 year. Hopefully he finds himself a good trainer and sports psychologist this summer and really brings it next season.