Re: Sadly, yes. Perhaps there is some correlation between the Google stat and these developments?
That's an interesting question. My assumption about these searches is that they are reflecting the consumption side, not the creation side of fanfic. So while I have heard these rumblings about, say, the Buffyverse fandom (and there's no question it has contracted since 2005), we see that searches for its fic is still in the top 10. By contrast, SPN fandom, which is going great guns and turning out every kind of fanwork by the bunches, is still only in a breakout category.
So my hunch on this is that fanfic has been a generational fad which has reached its peak and is passing. By that I don't mean that fanfic began with the Internet or that it isn't always going to be with us. But I mean that for the generation of kids who were in their teens over this last decade, fanfic has become a very commonly known phenomenon, and like all fads, there was a surge of interest in it which may be passing because (1) all fads do, and (2) they have become more occupied, as in your case, with offline commitments.
I would expect that a sizable number of that generation will continue to read and write fanfic, or may come back to it at a later date (possibly much later). I just think that the "everybody's doing it" phase may have passed, and the novelty of the issue to those outside fandom is also passing, and as a result of both things, overall searches are declining.
I'll also go out even farther on a limb and attribute a lot of it to HP. As we all know, it was the 800 lb. gorilla of fandom. With the books now finished, you would think that this would cause a greater desire for fanfic, since canon is fairly closed. But I've noticed that the opposite tends to be true, and people tend to move onto other fandoms rather than getting an influx of new blood when a canon ends.