At 5'11'', 185 lbs, he is the exact same height and weight that Anthony Duclair, Tobias Rieder, Claude Giroux, Calle Jarnkrok, and Carl Hagelin currently are.
He is already a few pounds heavier than Jordan Eberle currently is.
If he gains a few pounds, he will be in the weight class of Jonathan Drouin, Joe Pavelski, Bryan Rust, Sven Baertschi, Nail Yakupov, Matt Duchene, and Zach Parise.
Some current 5'11'' centermen in the NHL: Sidney Crosby, Claude Giroux, Tomas Plekanec, Calle Jarnkrok, Derek MacKenzie,
Leo Komarov, Joe Pavelski, Sam Gagner, Matt Duchene,
Marko Dano, Andrew Shaw, Torrey Mitchell, Vlad Namestnikov, Blake Coleman, Casey Cizikas.
5'10'' centermen include:
Robby Fabbri, Vincent Trocheck,
Mikael Granlund, Matthieu Perreault.
Nick Suzuki is already 185 lbs and will become heavier. He turns 18 years old in August.
I don't see size being an issue for him. Size was an issue for Hunter Shinkaruk, who was 5'10'' and 175 lbs when he was drafted, but also 10 months older than Suzuki will be at the June draft.
Unlike Kailer Yamamoto, who is 5'8'' and 159 lbs, Suzuki's size does not put him at any significant disadvantage. If a team believes that his game has the qualities worth taking at their draft position, then his size should not dissuade them.
Here is another scouting report; this was written in May 2016:
http://hockeynow.ca/blog/prospect-profiles-cody-glass-nick-suzuki-dereck-baribeau-