My new theory regarding season 8 and current events...
* Buffy has become mystically merged with the Scythe. Buffy had the Scythe when she was picked up and dropped by the goddess. I asked Scott Allie if Buffy recovered the Scythe after she woke up in the snow with her superpowers, and he said "She did not." We haven't seen it since... nor has its absence even been mentioned, oddly enough.
* It is the Scythe, not Buffy, that is sucking up the power of dead Slayers. The Scythe is the conduit for the Slayer magic. But since Buffy is merged with the Scythe, she's getting the "benefit" of all that power.
* The Slayer magic is now actively trying to return to its normal state -- a single Slayer. The magic -- which is primarily demonic in nature -- is responsible for the increasing violence against Slayers around the world, as the magic tries to kill them all off and re-consolidate their power. Twilight is not the one directly responsible for the recent mass murdering of Slayers.
* The magic is now spinning out of control, and the only way to save the world now may be to separate it from the magic completely... the banishment of demons, vampires, and magic (including Slayer magic) as depicted in "Fray."
So the real "Big Bad" of the season is the Slayer magic itself.
I ran this theory by Scott Allie and got a "no comment," so who knows? Maybe some of it is one the mark.