All this probably needs is to be put into perspective. With other Sims, the typical life span is actually very short in relation to LFS.
But in all honestly it's just the nature of gaming. Does GP4 or rFactor still enjoy the user traffic that they did when they first came out? I doubt it. Even NR2003 is pretty much gone with the exception of a few odd leagues.
The only reason why LFS is still relatively active is because of it's fantastic patches but of course as time moves on, people will start to expect more and I think that's very natural. (The fact that the recent patch is delayed doesnt help so the increased amount of complaints is natural as well)
I have no idea if LFS will even return to it's former glory or if it will just become another "dated" game in the eyes of the public among the likes of Anarchy Online, M.U.G.E.N., Super Mario War, Frets on Fire, rFactor, etc. (Which are or was in a similar situation that LFS' going through now)
But the first step to avoid that would definitely be to improve the system. The Scirocco and the Rock is a very nice addition. In fact, I'm eagerly awaiting the Rock's oval myself. But it's come to the point where I would gladly sacrifice all that just to have better contact system, fixed buggy barriers, better (not necessarily more complicated) immersive sounds (crashes, engines, etc), a damage system that is atleast remotely accurate to real life situations.
And of course, new environments and maybe a graphics update would be nice. This will attract more players.
I understand that the devs can do w/e they want and if they want to focus all of their efforts on that car and the Rock then fine. Finish it. But LFS's more glaring problem better be addressed if not in the next patch then the one after that. Or else LFS will become very stale and wither away. It's happened to just about every game except for the overly hyped ones like Counter-Strike or Starcraft but LFS is certainly not one of those games