You should never messure a game by how many Posts are being posted at its forum. If that was the case, than a great many games would have been viewed as dead long before they were. (Armada, Tribes, Dark Forces, Rebellion, BOTF, Wing Commander, Decent, Freespace, Soldier of Fortune, DeusEx, Elite Force, Half Life, Diablo, Starcraft, Warcraft, AOE, Civilization, SimCity, etc.) Each of these games had forums that died off or slowed down long before the games were ever considered dead. And in fact many of these original games are still running very strongly with sequals, or in original forum. BOTF is still being played and discussed actively on some Trek Game forums, as are many other games.
No, SEIV is no where near death yet. It still is drawing in new fans each and every day. As for DO, well, it was a fun first game of that type from MM, and my nephews love it. In fact, my neighbor even bought a copy because his kid was over and played it and liked it.
Periodically throughout the year, the forums die down a bit, that is natural. But they always pick up when nothing is going on. People love to chat about things they enjoy doing, and SEIV is damned enjoyable IMHO.
