Considering Marek's network of people and how it's worded, it is most likely a CHL source and a 1st rounder picked between 2015 and 2017. I'll rule out anyone who played an NHL game this year.
That leaves a list of basically.
Jakub Zboril, Zach Senyshyn, Olli Juolevi, Mikey McLeod, Jake Bean, Logan Stanley, Kiefer Bellows, Dennis Cholowski, Julien Gauthier, German Rubtsov, Max Jones, Brett Howden, Sam Steel, Cody Glass, Michael Rasmussen, Owen Tippett, Gabe Vilardi, Cal Foote, Jusso Valimaki, Robert Thomas, PO Joseph, Morgan Frost, and Jokiharju. Now, maybe they mean they won't be full-time NHLers which adds people like Dylan Strome, Logan Brown, etc.
I doubt its a 2017 guy, but how many teams would be considered very prominent? Boston, Philly, and Detroit are all very prominent American clubs. Given its Sportsnet though, it could also be referring to any of the Canadian clubs.
If I had to guess, I'd guess its one of the two Bruins from 2015, but I wouldn't say it with much confidence.