Thats kinda what I am saying. Its written with the intent that if its not a success, then the story at least has and ending, but it does lead you to think "what might happen?", but at the same time it also gives you the possibility for a sequel.
The first Star Wars is a prime example of this as well. Lucas and Fox knew that a sci-fi movie was a risk in 77, so the story had an end, but at the same time, the reason Vader was left alive was to make sure that if it were a hit, the sequel would certainly follow.
It was written with sequels in mind, but had an ending that at least gave you a degree of closure on the story if it ended up being a solo film!
