They’re waiting for someone to pick them up and go places. KA101 was our last big contributor to them, but hasn’t had as much time to develop things due to being our amazing main merger (round of applause). Before that I was the previous big mycus guy, and before that they didn’t exist as much more than just fungaloids and spores. 
It’s pretty much just waiting for someone to come up with a good extension or implementation of the existing lore, to PR it, and to go from there. There’s some littler things that could be done (like maybe an aesthetic change) and bigger ones (allow for the game to update the map post world-gem, and then have spreading mycus start to bring in larger, more dangerous mycus creatures), but there are plenty of options even just looking at the current lore in place.