The lawsuit doesn’t have to succeed in court for Epic to succeed. If the case generates enough publicity but ultimately fails, they may be able to lobby Congress for a new law akin to the Magnuson–Moss Warranty Act [1]. Then, instead of precedent they might have statutory protection for what they want to do.

[1] https://en.wikipedia.org/wiki/Magnuson%E2%80%93Moss_Warranty...