Trixy! You're from Quebec, aren't you?
Costumes to expect? Umm... Well, there's no way to know for sure. A lot of people change their costumes every year!
Last year there was a lot of FMA, Bleach, There's ALWAYS a lot of Naruto, I still saw a few characters from Chobits this year, Um...
Because it's CN and CN's not all only anime, You can expect to see some trekkies, and other sci-fi fans, comic book cosplayers, Horor cosplayers, lolitas, Video game characters (there might be a few soul calibur cosplayers this year, and you can DEFINATLY count on a lot of Final Fantasy/ Advent children costumes this year!)
I'm hoping to have a .hack//Cosplay, if other people want to dress up like .Hack// Characters one day of the weekend!
But really, you never know till you get to the con!
Just keep checking out this forum. Usually people like to post who they're going as, to look for people from the similar series to join their group photoshoot(s)!