But guys! Sully discovered Drake when he was rather young. Drake could still be in the game they could just move the story to something that happend before. Unlike God of War and other games, the adventure and interaction between characters is what makes Uncharted so lovely. Most games have a standalone kind of adventure, so really, they could even call it Uncharted 4.
Maybe one level features a circus which is where we can see Drakes fear for clowns hahaha