Was this the last OHL game Galchenyuk will play? It's possible.
With the way things are going, there doesn't seem to be much more that Alex Galchenyuk can prove to us at the OHL level other than consistency. With 58 points in his last 29 games, Galchenyuk has been scoring at a 2 points per game pace since the beginning of October.
This 5 point night, including a hat trick, was his final game before joining Team USA for the IIHF World Junior Hockey Championships in UFA, Russia. By the end of that tournament, if the NHL and NHLPA come to an agreement, he will most certainly be called up to the Canadiens for training camp, and likely get the 9 game tryout at the very least.
With the lack of depth the team has at the left wing position, which is where Galchenyuk has been playing this year, it's very possible that he will make the team. Not only that, but getting into the the NHL this year will make him a better player next year, as there will be less of an adjustment period then.
Watching Galchenyuk this year, it seems like every goal he scores involves a ridiculous amount of skill. A few scouts have called him a defensively responsible Jason Spezza, and despite what you may think of the Senators, this is a really nice comparison, Spezza is a great player.