David Morrison just hosted Carnival f Evolution #52, and now he has written a post with lots of statistics of CoE: The network history of the Carnival of Evolution.
In short, we're doing quite well compared to many other carnivals who have gone extinct. This is especially true for science carnivals, of which CoE is the only active carnival listed on BlogCarnival.com.
The steady growth of CoE through time. "Fortunately, the number of posts has shown a steady upward curve, as indicated in the sixth graph, although not always at the one-blog-post-per-day rate set in the earliest days. However, over the past 20 Carnivals there has been an average of 1.06 blog posts cited per day of passing time, so we are certainly holding our own."