I don't think that the governments can really stop any anonymous cryptocurrencies unless there are specific mandates, policies and regulations purposefully put into place that would stamp out any cryptocurrency to fiat conversions. That would really stifle the scene and people would start panic selling. Instead I believe organizations like the SEC, CFTC, the treasury departments and congress will each issue some sort of small amount of guidance on to to proceed lawfully within these sectors. The toughest part is to prevent the strangling of innovation while still maintaining balance and order.