I don't think Joss has to do anything. The relationship is dead in the water already, and all Joss has to do is leave it that way. There are lots of things S9 could do to annoy me, but the things I hate about S8 (and am deeply ambivalent and unhappy about in S6 and S7) ultimately the fault of the writers, not the characters, and so I can still enjoy other interpretations of the characters in fanfic.