Seen it happen with a small online indie game community I was a part of before. To make a prediction from what I remember of that: First there's a gigantic RIP thread. Community tries to get all the information they can about the few who know anything about it at all (Though this is parallel with anything pertaining to Blockland's future, see: v9, v11, v21). Everyone does stuff - builds, add-ons, videos - as a tribute to Badspot.
After that, community begins to drift apart, as no progress is made on the game. Moderators go do their own thing, forum members go find something else to spend their time on, though a few stick around to try hopelessly to keep the community alive. I imagine specific in our case, add-on devs that stick around would try to create large scale projects to try and revive the community with themselves in a position of respect, but the game would die off pretty soon when key distribution breaks or gets shut down.
Drama forum would probably dry up a bit as the forum develops an aura of melancholia. Much further down the line is anybody's guess. The Blocklanders Steam group would probably retain most of its members - even though people would drift away from the forums, they probably wouldn't purposely sever ties to the community. Going back to big-project add-on devs, sometime after it's over someone will probably round up every member they can still contact and announce another huge revival mod - this already happens with Age of Time. Of course the mod dies too.
tl;dr community collapses, people cling to it, they fail, everyone goes home,
Edit: Got sidetracked and forgot I wanted to post this as the end of my tl;dr before I hit post:
https://www.youtube.com/watch?v=_hZrXdJ-ibo
