Many already are. This notion of all this under the table stuff is bull. The bill is still bad. It must be defeated, but the idea that these folks are paid under the table is fantasy.
Do you think all the day laborers being picked up around Home Depots and numerous other locations are working for employers who fill out all the required forms, withhold FICA and other taxes, i.e., and keep all the records employers are required to keep on their employees?
Many are paid under the table and many probably work fewer hours for many employers than would require withholding, and it's likely planned that way.