Say Yu Jin was not worried that Pang De would ellipse his reputation by killing Guan Yu and did not ring the gong so Pang could not finish off Guan after he was hit with the arrow. What do think would happen.
I think that Guan would have surely been killed and Jingzhou overrun by Wei. Then, since Wu had not helped, Wei would have kept Jingzhou. Pang De would be elevated to a very high generalship, up there with Zhang Liao and Xu Huang. Yu Jin would have also been promoted though not to the extent of Pang. Now Wu would try to get Jingzhou back as would Shu, and there would be a three way struggle for Jingzhou. Shu and Wu would not ally because of their own greed for the land. Wei would come out victorious because Wu's attack was fueled by greed and Shu's attack would be fueled by an overwhelming hatred and want for revenge for the death of Guan.