Definitely not. If Imu is defeated, even killed, the other four Gorosei go with him, and the Holy Knights lose their powers, and him gone before we even learn about the truth of Void Century is quite far-fetched.
No, I can't forsee a true defeat. More then likely, the pendulum shifts in his favor, but he expends too much energy and his illness catches up to him.
Because that's also what we need to remember. This isn't even his true strength, saved for Round Two at Mariejois.