His name is Twilight, so that's a pretty good name for the enemy of Buffy the Vampire Slayer. Twilight is the opposite of dawn. The Ex-Key Dawnie hasn't been herself lately--and even now that she's been returned to her usual shape, she's not acting quite right. What's all this smoochy business with Xander?
Well, I'm not going to predict that Twilight will be revealed to be Dawn. I'm not going to take the bait. But who else could it be? Is there anyone important left? Cordelia? Jessie from the pilot? Kendall Casablancas?
Anya. She would be my choice. I mean, I hate the temporary deaths of comics as much as the next guy who buys the death stories anyway, but if Spike--whose final exit was my greatest source of joy in the whole series--didn't stay dead for more than a few weeks, why should the delightfully odd ex-vengeance-demon who didn't irritate me at all (unlike any number of cocky over-sexed leather-clad contrarian types in the Whedonverse)?
Twilight is Anya. It's settled.