Well, it seems that Sony's not even calling it done as they've just released an update to the app adding an entire new chapter with a new puzzle mechanic. You'll find 45 new levels in King Toera's Golden Tortoise and even a nod to "big" nate, a joke that a developer once made in Uncharted that is now a skin in Fortune Hunter.
Uncharted: Fortune Hunter gets updated with 45 new levels and a big Nate skin
Uncharted: Fortune Hunter's already contains a great deal of content, especially seeing that it's free. Yes, it's used to promote the release of Uncharted 4, but it doesn't have to be this big or even this good.