Kronus cut off his balls and apparently he is dead??
Immortals can't die, and for an immortal as powerful as he is I don't think getting his sack chopped off would stop him.
Also the Protogenos (primeval divinities) cannot be defeated only kept asleep.
Does anbody know?
And if RR made a sequel series to HoO it would be pretty cool if Ouranos started re-forming.