What time frame are we talking about here? If you look at the server history the highest number of licensed racers online was 764 in the last half year. That number was reached around 40 days ago (when were the new sounds introduced?), and has indeed been dropping since (1 month=674, 1 week=580). However, keep in mind that spring is coming (at least in the northern hemisphere), so there's likely to be a little less activity. Also, the latest patches (V to W) have been out for some time now and a new patch usually leads to more racers. So I'd expect the number of racers to rise considerably with the upcoming multiplayer incomp patch (whenever that might be). And afterwards figures will go down again. However, after each new patch that changes things considerably, the numbers will probably stabilize on a higher level than before the patch (at least that's what I think and hope). Unfortunately, the LFSW statistics don't seem to go further back than half a year, would be interested to see how figures have changed over two or three years.
(and yes, I don't have much to do at work today, so that explains the lengthy post about nothing :tilt