The Government of Australia handles the country's video game ratings. They have released their rating for Star Fox Zero, giving it a "PG" rating. This rating is probably closest to the ESRB's "T" rating.
Perhaps more interesting than just the rating is the Consumer Advice which says that the game has "online interactivity."
This doesn't mean much more than SFZ will have some kind of internet component. It could be as simple as Miiverse integration, though, so I wouldn't take this as confirmation of online play.