A ban like this is certainly possible, even likely. Bitcoin holds serious threats to so many aspects of government operation.
However, it will be like banning the internet - the rest of the world will just laugh at you. Bitcoin et al is the future.
BTW have you seen how the war on drugs have gone - you can make pronouncements to ban things, but you cannot stop them, especially when they are so good.
Also there is potential risk of civic unrest if people ban something which many perceive as legitimate - it would be like seizing assets.