The Chu arc and the last boss arc could very well last up to 200 something chapters. That's 4 years worth of weekly chapter releases right there.
I will be thoroughly disappointed if it doesn't at least top Gyou's 150 chapter arc.
If anything that Gecchi Plains taught us, that Chu is riddled with Great Generals left and right. There's no way that with a certain historical antagonist I won't name, Chu would have at least three Great Generals (Kouen, Karin, and Plot Twist) and worthy of rivaling Ousen/Moubu/Tou, and one worthy of rivaling Moubu's strength (Man'U) and two young generals meant to be Shin's rivals (Kouyoku & Hakurei)...
Needless to say, a Chu war arc has to be over 150 chapters long. I know that Haru is just a man but it'd feel underwhelming if it was anything shorter than Gyou.