I haven't been around nerd as long as some, so if some of this has been tried before I apologize.
Some ideas:
1) clearly state the end date (with the option for additional length if players vote) with some sort of large event closer to the end to give people something to work towards
2) I know for me, not having a purpose makes the game slow. And the ender dragon isn't really my cup of tea. I think additional group events would Hold people people later on. Maybe there could be some sort of building committee for each event (i e scavenger hunt, maze, 5k). The event server is amazing for large events that tend to be staff-created or lottery created, p would be an excellent place for group-sponsored events. Even little things like argoths "Sunday night violence" or white oaks "secret Santa" felt much more group-oriented and fun and gave me a reason to work toward something rather than just building.
3) netherportals. I understand not everyone can make their own, that would be chaos because we'd have them every 5 feet. But on a map this big, maybe a second ring of portals closer to the edge, I feel like i never go that far because horses are really laggy on my internet and I am not running way out to the edge is be gone all day. I love the huge map, it's just hard to access some of it.
I joined nerd because I love the community. I love being able to build things and then share them with people or share things they have done. #2 is my biggest wish, I can play minecraft in singleplayer if I just want to build. I play on here for the people.
Edit: because my phone puts weird autocorrecty things in
