Until last Friday, when it perked up a little bit, and put out a couple more chiles. The plant itself continues to look pitiful, but slightly better than dead, and the chiles are continuing to grow. Meanwhile, the cayenne hybrid (three feet away) is throwing off oodles of ripening, hot, somewhat underflavored little chiles.
I think the serrano is a zombie plant. My younger son thinks that if we sneak out into the garden at night, we'll hear it saying "seeeeeeeds" and trying to eat the chiles from the hybrid (and the nearby tomatoes). I think maybe letting him see Shaun of the Dead may have been a mistake. Or maybe not.