I just looked at the nQuake download statistics...
The period November-January saw 14 percent less downloads of nQuake than the same period a year ago. However, the period August-October saw only 1.2 percent less downloads. Speculations? Is QuakeWorld dying slower or faster than you thought?
Perhaps the reason of lesser downloads is, more people wanted to try nQuake out a year ago (due to it being relatively new), and have no reason to download it again this year. That is, the share of newcomers downloading nQuake could be more this year than last, which could mean QuakeWorld is not dying, but growing.
Or perhaps nQuake downloads is not a great way of estimating the amount of health QuakeWorld has, but simply a way of seeing how often people are cleaning up their QuakeWorld folders