Only shot at BB being final villain is if he’s the shadow in the third world that remembered the promised day. So, Oda will turn the yami fruit into the Earth God or some shit. Imu seems to be the forest god so I don’t know how everything will play out. Then again, BB can be none of those things. Easier route to pull off is to just pin the blame on Imu for everything. He already oppressed the world for a millenia, BB can’t outdo the weight of that sin unless he’s secretly the primordial god or something.