They won't outlaw Mt gox. That makesn o sense. They woll outlaw trade and possession of bitcoin because of money laundry and being an alternative currency. US citizens are required to use the USD. It is illegal right now.
Could you cite your sources please?
Regarding required use, I could not find it quickly but I am pretty sure no second currency is allowed.
Regarding laundry, look at
http://bitcoinlaundry.com/. I steal money from a bank, buy bitcoins, launder them and cash out to USD. Easy.