That will depend on which exact cosmology you're using. For example, The Great Beyond (PF, Golarion) uses a lot of "high function divinities", which are basically the embodiment of either a cosmic principle or one of the laws (nature, physics, you name it). You kill the deity mostly known as Pharasma, than that's it with birth, death and the judgment of souls for the whole multiverse. Finito. Because she is those functions - that's quite different from "low divinities", like, say, Thor or such.
(For example, the patron deities of human and snake folk wanted to duke it out, they killed each other and both their races went into decline, empires fell and, the human god being also the representation of prophecy, functional prophecy also died in that game universe. It just doesn't function anymore)