Anything they put in the work to implement in a test server is already going to be something they plan to put in the real game. They aren't going to put time and money to implement wacky forum ideas for new game mechanics or systems just to see if people like it, and then maybe throw it out if it doesn't fly.

Also, the kinds of players who would participate in a FFXIV PTR are, um... well, I'll be diplomatic and say they are "not representative of the overall population." Square Enix should not base their decisions on the course of the game based on feedback from a tiny minority.