The thing is it can’t be kyoshiro cuz We know he was under hyo so when orochi and Kaido took over Wano kyoshiro took the chance and sided with orochi and he himself became yakuza boss and is with orochi since then everyone knows about him .
But there is the possibility of him being the traitor but shutenmaru should knwo that since he was there so kyoshiro is out for now.
Koshiro is in the air but can be explained and tie it perfectly actually cuz we can assume he travel to east blue to fine his family and made his own family he got back for one last time to see oden and tel all about it and that’s when all happened and then he left to eat blue and was waiting 20 y for the prophecy to go back and as we saw in ch 0 revision where in his village so he might bring Revos for help and we can learn about Sabo also to tie the story better and get some answers on some questions.
but all this are speculation nothing solid but story wise I lean more towards koshiro is more exciting
#teamkoshiro