If dark matter is proven to be a crock, they will move on to their next hypothesis: A wizard did it!
Trying to avoid all the implications that would occur if celestial mechanics (Newton!)is wrong!
My bet is before that happens they’ll detect something that sort of fits the current theory or a serious addendum to celestial mechanics theory will be found.
If dark matter is proven to be a crock, they will move on to their next hypothesis: A wizard did it!