should be obvious

because he's small fry

i think he gets killed at protecting his friends

Something emotional that'll all make you cry
Then he'll come back to life

And thus comes another 500 episodes

Assuming that he has achieved a high status in the World Government
Coby will do something that is not in favor of the World Government like expose the World Government of what it's done during the Dark Ages
then get his ass kicked by these guys http://onepiece.wikia.com/wiki/Gorosei
Then Luffy comes saving Coby's life while defeating the Gorosei then dies
Coby will recognize Luffy as king of the pirates.
W.G and pirates call a truce.
and this all will happen right after they find One Piece.
THE END.

A new series will begin as Coby's son as the Protagonist
the story will be about how fucked up everything is about the world and how pirates are no longer the pirates they were once
so he'll rise to the top and renew a world order.