i've certainly been reading femlsash since the heyday of Xena and Star Trek: VOY and ER (remember Kerry/Kim and Kerry/Sandy?) but i wasn't really active in the fandoms as a writer, so i can't really say where they've gone. i'd be willing to bet that a lot of the BSG femslashers are now into other sci-fi shows with queer content like Warehouse 13 and Lost Girl. i'm guessing the Harry Potter fans have moved on to other book fandoms with interesting female characters like ASOIAF and Hunger Games, maybe even AtLA and Legend of Korra. perhaps the ER folks are into Grey's Anatomy and Rizzoli & Isles. these are just guesses- i'm kind of a bad person to ask as i'm mostly a small fandom femslasher.