Honestly, Muzan's fecked. Even if he manages to survive this battle, his body is irreparably damaged and he'll likely never be as strong as he used to be. Even Yorichii's scars remain on his body - I can't imagine what kind of scars this beating would leave on him.
Also, still rooting for the "literally everyone dies ending".
Also, I wonder if Tamayo will become the next Muzan. She's capable of making other demons and has the will to continue existing even after Muzan absorbed and destroyed her.