There are many miners spread all around the world and just as many merchants and bitcoin users. China might dominate
Bitcoin mining, but they are not the only miners/users/merchants. We will take a huge hit if we lost China, but we will also
not go down without them. Asic chip manufacturing will have to move to Silicon Valley, if the Chinese market stops.

This worst case scenario can be possible if the world will have the World War 3 happening or a similar conflagration can happen which can affect all of us. By then, everything will come to a halt and our Bitcoin can even mean nothing as there would be no internet and our gadgets can be useless especially if the source of our power can be disrupted.
I am sure that there are a group of people who are thinking of this possibility and they must have a plan -- a contingency plan in case a major disruption of our technological infrastructure can happen. Hope there would still be an effective communication backbone by then.