"Qie Shi. Make sure that He Shun, Wen Wen, Chen Yu, and Fei Huo rest well before they all depart for their respective regions." Cheng Sheng spoke after he treated Pai Lie's spirit and gave the Righteous Alliance the medicine needed by Pai Lie. As for Zheng Fu Gong's illness, he has already been handed the book needed by Cui Xiang to learn to treat Zheng Fu Gong.
As to who will replace Zheng Fu Gong as the leader of the Righteous Alliance while Zheng Fu Gong is recuperating, it would naturally be Jing Rui. There is no other sect leader that could replace Zheng Fu Gong as the leader of the Righteous Alliance, as that sect leader has to be very familiar with how the Righteous Alliance works. Only the Zunjingde Sect is the closest to the Righteous Alliance, and that Zheng Fu Gong has already been preparing Jing Rui to replace him as the Alliance leader.