I think it is starting to matter now. One of the main reasons that Trump gets away with so much is often because these NDAs do not allow their subjects to say anything about it. If there the NDA with Daniels is invalid and she comes forward and tells her side of the story, which Trump has never allowed to be told by any opponent he's ever had, women will listen. The GOP has forsaken all of their morals, but I still think that GOP women will care that Trump married Melania, had a child, and then was out banging porn starts with impunity.
At a bare minimum, it's more fodder for attack ads for Dems in 2018.