The government will never allow that since everyone knows about the dollar, while not that much people know about bitcoin and it's also limited and can fluctuate way to quickly, the government wouldn't like their dollar going up or down by hundreds every day, that's way too insecure.
Yes this is what exactly some of our mates are not ready to understand but honestly speaking denying this truth about the dollar will be insane.
Being realistic I understand that the dollar has its own place in the economy which cannot be that easily mitigated by the Bitcoin which have many flaws. The Bitcoin is the new financial system, with a number of flaws which can be neglected by the individuals, but not by the institutions.