I think it's pretty easythe end of the film dramatically expands its world, shifting their entire culture to one of exploration. It makes sense that this exploration would lead them to discover new islands, but also potentially new people, and there's easy sources for conflict there. It seems logical that they have their own mythology, and perhaps even their own demigod, which might give both Moana and Maui someone to grapple with. Make her rival male, his female, and let sparks fly.
I was more referring to scale of conflict. I don't think any Disney Princess movie has ever had stakes this high.