I think not, so an average person will not be using bitcoins, except maybe for some illegal stuff.
So declaring bitcoins illegal will end bitcoins as we know it today.
This is true, if you are thinking in the old way where nations mattered. Illegalizing bitcoin transactions would only be possible under a one world government. Bitcoins could be made illegal, but then you could probably sell all of your bitcoin on an exchange somewhere like Vanuatu, Tajikistan, or Cape Verde for the next crypto currency. Since it seems to take a few days to generate cryptocurrencies there could be an endless string of them. As has often been observed on this forum, the only way to kill bitcoin is to kill the internet.
A good metaphor would be riot police with shields and clubs standing next to the ocean and trying to stop a tsunami.
The only way for the powers that be to retain control will be a one world government with immediate arrest for any evidence of an off book transaction. This is not implausible. This is WAY bigger than the Protestant reformation, and that resulted in hundreds of years of war...
semaforo, you are a very inspirational