If Kaido doesn't die, he will come to Wano again unless Oda removes kaido's brain. It's not like he gonna be defeated in 1 vs 1, so if you are Kaido and Wano needed many people to take you down then you know once the ennemies will leave Wano, he can just come back and rule it like he is actually doing. Momo and scabbards are gonna stop him and his crew ? lol! The fact all the WG are together, is a golden opportunity so next time they won't have it unless another big preparation to face Kaido and his crew.
Even if Kaido is defeated, gang banged in this arc, he will be still the WSC so no one can beat in 1 vs 1 and also his crews will be fully healed. Best example is Jack, defeated many times but still coming back and doing bad things.
BP is crew of real pirates, they love to kill, torture, raid. Oda needs to remove Kaido (either be killed or be in prison for ever) from the story. Because if he is still there even alive, how Luffy the MC and the future PK could claim that he is stronger than Kaido ? Because we don't even know if EOS BB could be stronger than Kaido.