I don't know if there will be more or not, but I do see this as standing on its own legs. If/When there's more, I would pick up from the end of this. Spike wanting to protect his angel while the elders would, no doubt, be horrified at his audacity in leashing an angel. The younger ones who summoned her wouldn't want to be faced with the horror of their actions, and no one would be comfortable with such a powerful creature in the middle of the village. Yep, there is either a lot of material for imagination or for a sequel.