Maybe something they will add in through the free updates? Cause I'm honestly pretty sure we know almost everything about the base game coming out on the 21st (other than the story for Single Player) but I do agree that there will probably be another Ranked mode.
EDIT: Also, just saw this somewhere else, but what if Pearl and Marina are really evil and since Callie is currently gone (and Marie is too, out looking for Callie) and are basically key to the plot of how Callie went missing. Basically, they helped take Callie out of the picture, thereby taking Marie out of the picture, and basically dethroning the two in order to establish their own dominance over Inkling society and Inkopolis. And I mean, Marina is already an Octoling, and Pearl looks kinda evil so...maybe? Or, maybe it's just a crazy theory I found on the internet.