Adding in my idea:
So it is said that he wont die until the sun touches the bottom of the ocean, which to me reads: when our sun dies and in its last stages of yellow sun, it expands into a red sun, thus enveloping all the way out to mars' orbit (or 'roundabouts). Making that about a couple billion years from now.
My solution?
Throw King Corb into a pocket dimension of the Nevernever and lock him away there until such time passes and he's released right as the sun expands. To him it's like no time has passed, yet billions of years go by on the mortal plane. This has been discussed in the DF about the fae doing this to mortals, but only in chunks of a few years to several dozen.
Removes the asshat King Corb from everyones lives, and follows the prophecy.