The traitor storyline has become one of the biggest plotlines in OP history (no exaggeration).
Just think of it: Oda has been carefully setting it up for almost a decade (!) now. It all started back in PH (2012), when Kinemon told them that he, Momonosuke, Kanjuro and Raizo tried to flee Wano but somehow the enemy knew their plan and chased after them. Then things got even more suspicious in Zou (2016) and intensified even more in Wano (2018 - present). Now we're obviously only a few inches away from the climax.
I think Oda is going to present a major twist/shocker when the traitor is revealed.
The most logical choice is Kanjuro imho. He would make sense and certainly have an emotional impact. However, I wonder if him being the traitor would be Oda's style. He left many obvious hints in that direction and I keep wondering if those weren't a bit too obvious.
So I will ask some questions, while trying to figure out the traitor:
1) Why is the traitor so loyal to Orochi?
We've seen that basically ALL of his subordinates think of him as a joke and ridicule him behind his back. Literally nobody we've seen so far would take a bullet for him. Yet the traitor obviously takes great risks trying to inform Orochi and snitch on the alliance.
So what is his/her big goal? What does he/her gain from keeping Orochi and Kaido in place?
2) How come that nobody has a clue about the traitor, despite him/her already being active for 20+ years?
We know the traitor already snitched on Oden back in the day. He or her is already active in the present day. In all those years nobody seemingly got a clue about the traitors intentions. That means two things in my eyes: The traitor is a damn good spy and actor and nobody suspects him/her at all. Like ZERO suspicion, not just "nah, this is a cool dude, he/she won't betray us!".
3) How does the traitor deliver his messages so quickly?
Kanjuro would be the easiest answer to this question, but hear me out: If Kanjuro really is the traitor, how come nobody has ever seen him send one bird-drawing (or something like that) to Orochi for more than 20 years? I mean he/she must've delivered hundreds of messages to always give updates for Orochi, it would be very fishy if Kanjuro dialed up several of those drawing-messengers per day/week. Somebody should've noticed such suspicious behavior during those 20 years imho.
4) What is Toki's role in all of this?
Toki is one major mystery right now. We still know almost nothing about her. She pushed Oden to stay away from Wano and pursue his journey, even going so far as to threaten him with divorce. Oda randomly showed us the scar on the leg. It's obvious this scar will have a role to play. She has been in the castle for quite a while now and Kaido tells Oden that there is a spy at his castle. Given Toki's careful personality (she immediately recognized the human traffickers back in the day, too), shouldn't she have noticed the spy over the years?
Last but not least: Why is she so damn relaxed right now? She flipped when Oden wanted to stay back in Wano a year earlier, but now, when her husband and friends will probably die, she's calm and relaxed.