@asm00200:
What should happen after a Yonkou is defeated is a lose of territories. And when you lose control over most of what you control.. suddenly you're not on the level of the other Yonkou, and you're not even worth the title.
I expect a bunch of different pirates fighting for control (and controlling) over these territories after Kaidou's defeat.
Seizing a Yonkou's territories does not have anything to do with their strength. Their physical power and the immediate strength of their crew won't go anywhere. Sort of like a Whitebeard with no territories, but he still has his crew, his flag ship Moby Dick…you get the point. I'm just saying, he had to die for a spot to open up.
Even if a bunch of pirates take control of Kaidou's territories, I expect he'll rest up after his downfall from Luffy, then get to work to take everything back.
Regardless, I'm looking forward to see how Oda handles this situation.