Just like the weather, history, and business, I do think the writing world runs on a cycle. First the audience is wanting all things literary, then the world tilts toward the popular, then back to the literary, then back to the... well, you get the picture. Fanfiction works in much the same way, I think. Just give it time, the right promptfest, the release of Magical Creatures and Where to Find Them on the big screen, a new ride at Universal, the return of a universally favored fanfic writer to the fold, the sneeze of a butterfly in Argentina, and this wonderful fandom of ours will right itself.
Right now, I think the world of real life is just too busy for many of us. Take myself, for instance. Work has been crazy since January. One thing after another, requiring a little less writing time at lunch or having to bring work home over the weekend, has lessened the amount of time I have to writing. The ideas for stories are still flowing strong, it is simply finding, or making, the time to get them down on paper that seems to be lacking at the moment. That doesn't mean I'm giving up. And I hope it doesn't mean you are either.
But this doesn't mean the fandom is on its deathbed. It is simply treading though the valley toward the next mountaintop. Or at least that's what this daughter of the Bard thinks/hopes/prays.
In the meantime, keep your spirits up. Keep supporting those writers who are currently able to churn out wonderful stories (SS/HG ones in particular). Keep calm, hold still, and wait. Everything will work out just fine.
Long live Harry Potter Fanfiction. Long live Severus and Hermione. Always!