Volume is not the main thing to be considered here. If this is gonna be the future(which I wish) there must be legal regulations. If some people are gonna use it for money laundering or smuggle the dirty money, thisis gonna be a huge problem even for 200 billions. Forex is totally legal so if it is 97459743 trillion, there is no problem. People are gonna accept this blockchain system but it is gonna take time and after legalisation in the most of the world, it is gonna blow like the banks. Even faster cuz there is no need for a building everywhere.