They don’t have to change any rules, they just create new taxes that make Roth tax advantage irrelevent (e.g. tied to consumption rather than income). Income tax is not the only way to tax you. If history is any guide, there’re many creative ways to introduce new taxes. In fact, Obama just said he is considering VAT: http://news.yahoo.com/s/ap/20100421/ap_on_bi_ge/us_obama_tax
