I don't expect Vyatchanin to swim for the US despite that he trains here in Florida. I suspect he will offer himself up like a "free agent" and swim for a country that offers the most opportunities. The United Arab Emirates, perhaps?
I commend him for his decision - I would have no problem with American athletes doing likewise if it meant that they could finally take care of their families and/or support themselves.
From the Daily Times:
MOSCOW: Two-time Olympic medal winner Arkady Vyatchanin has decided to quit swimming for Russia and represent another country, the Allsport news agency reported Monday.