...There are a lot of possibilities, but the basic idea would be the same.
One of the most important posts on Bitcointalk. Pay attention, imho.
I`m afraid of that scenario really.
They could do the same thing as they did with gold.
They create a paper currency 100% backed by bitcoin & redeemable in bitcoin. Then they decrease the backing to 90%, then 50%, then 10%, then 0%, and create a fake bitcoin paper fiat currency, that would end up just like the current ones.
But in the meantime it would surpress bitcoin's growth and price. Just like the gold price is surpressed now with all the certificates and paper derivatives.
However, given that we live in a more and more digital age, this would not work as efficiently as previous fiat schemes. Most people would use the real bitcoin (not me)