That would be a good thing...but in that time they will destroy the “brand”.
My experience is that PCA and RP churches attract a lot of informed believers. They are not very seeker-friendly, “we’ll turn down the message for the guests” types. PCA will grow as they absorb the more traditional PCUSA folks, leaving the empty shell for the social crowd.
We have a local non-denom that is based on the Presbyterian model. Most of the preachers are local college professors and it is VERY conservative. We’ll probably see more of that.