Bitcoin's deflationary quality if unchanged will bring Trade to a halt, that's basic economics, and independent of how many decimal places can exist in a number. Nobody in his right state of mind wants Trade to get hurt. So before that happens, National Security will kick in and Patends, Licences and  bitcoin infrastructure will be seized and protocol will be changed.
IE I see the FBI raid the biggest pools and alter the miner to ignore transactions that dont divert fees to a FED wallet, thats all they have to do, not bureucratic shit, no forms, no checks, just a hardcoded VAT. More countries will follow and boundaries will be raised before you know it. Effectively splitting the transaction tree into a forest, without hurting the blockchain.