If you want some actual in-game lore that supports this theory:
"But soon, the flames will fade, and only Dark will remain.Even now, there are only embers, and man sees not light, but only endless nights."
"Gwyn, "Lord of Sunlight", who is the one who steps up and links the fire."
"In the war that marked the dawn of the Age of Fire, Gwyn wielded these rays of sunlight, which remains fierce even as they fade."