Yes, but that does not mean they need to destroy the unions in the process. I seen the right to work take place in two states. Texas employers took a stand to destroy the unions and lost the best apprenticeship programs in trade programs. The only unions to survive are the manufacturing, some building trades with very limited members, and govt.
If the unions want to exist, they must prove they serve a real purpose. Otherwise, the unions should go the way of bad corporations.