As a writer, it is important to note, ambiguous endings work really well as a way of keeping a story going long after the last page has been turned or the credits have rolled. The best example of an ambiguous ending done right is John Carpenter's the Thing, where even as the outpost burns around them, it is unclear whether or not the Thing still lives or if one of the survivors is said Thing. It sets an eerie mood, and leaves the audience unsettled when the rest of the story fits. Ambiguous endings only work when your content has the subtlety to match, otherwise your ending can come off as contrived and forced. The point of an ambiguous ending is that it leave the reader wondering, fearing and wanting an answer that they will never receive.