I've heard a few things about FH+ and have even seen a few but rare screenshots, most like back from when it was new to everyone, so it sounds like only but a myth.
There is however, or at least was, a small group of floofs who were working on creating something called FeralHeart Evolved, or FHE for short. This version of FH was to have new music, new textures, new maps such as a remade Fluorite and etc, including more maps added to the game than just the default few, new animations and all that fun stuff. I was asked to be a part of it some time ago and help with its creation, but the one leading the project when on vacation some time ago and has not been heard from since as far as I know, so to say FHE will ever be finished or released I'm not all too sure. But I am sure that if it ever is, it won't go unnoticed.