Is there a valid concern that worker protections enshrined in law might come under attack?

Constantly and always. But wealthy will never succeed in turning the labor clock back to 19th century work hours, child labor, sweat shops, death and injury rates, indenture, slave wages, or any abuse of human capital. But they do try. They try so much that in hard times they will manage to carve out a little regression in labor law. And every once in a while there is rule or law that has outlived its usefulness - like affirmative action quotas. But try as they might they never understand that the worker is equal to their customers, agents, suppliers, managers and intellectual property producers in the success of their business.