We've got 16 people just in the test game, and there are easily another 10 just sitting on the sidelines commenting in these threads without playing. That's 25+ without even doing much advertising. I think the probability of us starting with fewer than 30 people is essentially 0%. Sure, they may not all turn out to be very active, but that's just the starting number. More will join up later, and the game will be able to support an increasing number as it progresses anyway.

Activity will depend on how interested people are in the game. A lot of the late-game interest in KOTR was due to the general increase in traffic that the Throne Room started experiencing. Now, due in large part to the Hotseat games, it's a very active place. There are a lot of hotseat players who were not in KOTR, and all of them are 'active' because the Hotseat games require it in order to run properly. If we can drag a few of the Gameroom mafia fans in here as well, we could easily end up with 30 active people for a sustained period of time.