This was a really lovely thread to make, hopefully everyone's suggestions offers some help!
One thing I don't go a day without hearing is how users miss the old maps. Specifically, Flourite Plains. The way I heard it described was "Too much change in too little an amount of time". Now I'm not saying trash the update, because honestly, it's downright gorgeous, all these new maps, but maybe bring one or two of the old maps back, redecorated, but with the same heightmaps and such, so it's still the same land but better decorated. I'm convinced that bringing one of the most popular maps back, and perhaps removing one of the least-used maps in the meantime would bring a lot more people online. The majority of the stuff around them would still be new, but they could also have that sense of familiarity and home. I know it would take some work to do, but I think it would be beneficial to the community's numbers in the end.
Another thing I really think would help is Buffy's YouTube suggestion. Maybe not in the super near future, because it definitely takes time to set something like that in the professional sense, but having a YT channel wouldn't only keep current users interested, it would bring in a lot of newer users too. Teaser trailers and such give people thinking about joining a sneak peak at what the game is like, and an official channel is bound to get attention.
Those are just my two cents. Being repetitive again, but this was really a helpful topic to make!