I’m sure taxing Roth 401(k) and Roth IRA distributions @ retirement will soon be on the table too... don’t laugh... it will be proposed... I PROMISE.
You never know with these b@stards, but I think what would be more likely is a reduction of the yearly contribution amount. Only about 20% of eligible Americans fund Roth accounts, so there wouldn't be a huge public outcry if they messed with it..