So as we know, Kaido's crew is based off cards. You have the headliners, based off card games, the numbers based off number cards, and the calamities based off face cards. You even have joker, not technically a beast pirate but an ally of the beast pirates. All in all, Kaido seems to have all the different cards in his deck, except for one.
The Ace.
Now I'm not suggesting that Ace was secretly a beast pirate or that the beast pirates had anything due to Ace, but I do think that the ace card should be represented on Kaido's crew. We've seen in the past that different characters can have similar names, you have Tsuru and O-Tsuru, axe hand Morgan and Morgans, I don't see why you cannot have the ace of the beast pirates and the ace of the whitebeard pirates. Hell, perhaps they were even rivals.
But I think it makes sense for there to be a fourth, secret, calamity that most people don't know of. why is this calamity secret? I think it could be for many reasons, but ultimately I think that they are a spy and are involved in clandestine operations on behalf of kaido. They could also be the "Ace" up Kaido's sleeve, made secret solely in order to keep enemies unaware of him and hence make him more effective as a fighter.
Lastly, I think that the existence of a fourth calamity could help solve two issues.
- the traitor
the traitor, as of now, literally cannot be anyone. The scabbards were all sentenced to death and hence cannot be traitors. And literally nobody knew that raizo was in Zou and knew that Hiyori was in Ringo. the traitor has seemingly supernatural surveillance abilities. I think this could be due to his devil fruit. I theorize he might have some sort of mythical thunder bird zoan that could allow him to combine CoO with electricity to gain Enel-like surveillance powers.
- a warm up fight for luffy
Luffy has had a warm up fight in almost every arc. With him needing to beat a yonko in wano, I don't see why he shouldn't have one now. I don't think he should have a warm up against the other calamities as 1)they would be better as fights for Zoro, Sanji, Jinbe, and 2) they're all on onigashima, with kaido. And I presume Luffy will go after kaido once he reaches onigashima.
If Kaido had a secret beckman-like right hand who was sent to destroy the alliance, Luffy could have a chance to take on a low top tier and perhaps test out his abilities before the main fight. Also, we've yet to see what true zoan awakening is, and I feel like Oda would reveal that before the Kaido fight.
