There's more. You've beaten two of the 3 acts of the game, so there's A LOT more. At first I thought it was some post game quest line that was to just add some fan service but then minutes turned to hours and the entire games ending was rewritten, and we get 2 really epic pre-rendered cut scenes.
If you load up the game again you start in Argonia with a celebration occurring. After you you leave, Erik will tell you that if you're looking for more adventure he saw something South of Octagonia while they were flying around the world during the end credits. Well... that's if you ever care to revisit the game and find out how it all really plays out.