Well if the necklace goes on a squid and Duck/Ahiru doesn't find it and Drosselmeyer doesn't use his world manipulating powers to return the necklace back to Duck, that would mean the squid would become human.
And that means the human-squid would be able to become Princess Tutu. And then Drosselmeyer would laugh at Duck's plight as she struggles to find her place back in the story because she got replaced by a squid.