There's a petition for certiorari pending at the US Supreme Court asking the Court to take up the issue of "Whether it violates the First Amendment to appoint a labor union to represent and speak for public-sector employees who have declined to join the union." Uradnik v. Inter Faculty Organization [Briefs]
Kathleen Uradnik sought a preliminary injunction challenging the constitutionality of an exclusive collective bargaining representative in the public sector, asserting that “the University and State of Minnesota not appoint the Union to speak for her and not force her into an expressive association with it.”
The trial court denied the preliminary injunction, and the 8th Circuit affirmed in December 2018, having decided that Uradnik "cannot show a likelihood of success on the merits of her compelled speech argument."
The Supreme Court may or may not want to hear this case. This is a wait and see.