You mean an escape route for whales?
That might happen. The good thing is the coin is not USD name but still I think they will equal it to USD if converted.
There is no way Mark Zuckerberg will have another bitcoin like or ethereum like coin which is too volatile.
His company will be questioned a lot if that happens.
AML and other stuff will be glued to him if he doesnt follow the rules of the government he is in.
I think this would really not matter to Facebook gain, because Facebook has a userbase of over 2 billion people, and the people that may pick interest in Facebook coin are still within this figure, in which they already have their KYC done already on Facebook while they were registering on the Facebook platform, so there is nothing new about the KYC to tem again.
I think people will still prefer to use Facebook coin even when they are fully aware that it will run on centralization platform, Most stable coin they are using already like tether and the rest are also centralized coin, which I do not think that they have had issue with, other than the issue with bitfiniex, and for this reason, people may prefer to use Facebook stable coin over them.