It is known that Oda uses the story of Momotaro to parallel the Admirals and the order in which they are introduced. He uses their colors to indicate their Devil Fruit powers, and the animals to indicate their personalities.
In the story of Momotaru, he comes across a Pheasant (Aokiji – Blue Pheasant was introduced in chapter 303), next she comes across a Dog (Akainu – Red Dog was introduced in chapter 397) and the Monkey (Kizaru – Yellow Monkey was introduced in chapter 504).
Then in the second of the story, Momotaro befriends a Tiger (Fujitora – Wisteria Tiger was introduced in chapter 701) and later a Bull (Ryokugyu – Green Bull was mentioned in chapter 711).
The second phase also sees a monkey play with a crab which later attacks it. Then the dog tries to kill the Crab but it could only knock it unconscious. This crab (or another crab) later comes back and attacks the dog during the final phases of the story. This crab is none other then Coby. As we know that the last secondary color is Orange, which translates to Orakani. The color Orange is created through mixing Yellow and Red, which symbolise events later in the story. Also, the scuffles between the Dog (Red), Monkey (Yellow) and the Crab (Orange) allude to the same events.
As mentioned above how the Dog tried to kill the Crab, this event has already passed and will be repeated again later under different circumstances.
Thus, it means that Coby and Sakazuki will fight.