Korrasami IS CANON

HERE'S A COMIC TO CELEBRATE

Edit: To those who wonder why I think it is so very canon (and I do!) here's a a tumblr ask I answered to the same question. (SPOILERS!) And I'd also like to point out the name of the song that plays in that final scene: "The Love of the Avatar". AND I'd like to also add that one of the main creators of the show is reblogging Korrasami on his tumblr. Just sayin'. 
EDIT: Officially canon, confirmed by creators.