I wasn't around to see the game back in 2005, but I have experience with today's game, and I don't think it's going anywhere. The events we host at Lindenwood University draw in a decent player base, every time I visit an invitational there are plenty of folks trading tips and incredible stories, and Missouri players regularly travel miles to play in a game. It will last as long as there are moderators willing to devote time and energy into creating a good game.
I think what SM is seeing is really simple- traffic here died like a fish out of water the week after the HVZ homepage redesigned and killed the link to this forum. No new traffic + less old traffic = less posts = less responses = no posts, unfortunately. You may want to check out the National HVZ Admin Exchange group on Facebook. It is as active as these forums were in their heyday. I wish we could get back to this form of communication, but I don't think it's likely at this point.