Now, there are plenty Saviors, as we met Aladdin we learned that.The Black Fairy probably didn't want to take any risks, so she used all of the baby saviors / potential saviors to help her in her land.
Well, Rumple probably knew that. (He's kind of a know it all). Yeah, he did not know he could've been a Savior, but he knew that the Black Fairy is in a constant search for a Savior that can destroy her. So, when he made his deals with others, with his ability to see the future, he could know who could bring a savior to life. So he demanded some's first borns, to tempt his mother to show herself.
Why I think my theory is right?
First proof - When the Black Fairy cut's Rumple's destiny rope, she no longer wants him. She preferrs to search for a real savior instead of waisting her time on her family. (Which she could, she just did not want. She did not see the possibilty of a having a family when there is another Savior that can be a threat). As long as Rumple is not a savior or her enemy, she has no need of him.
Second Proof - Regina was a Savior. She saved Storybrooke from Zelena on the third season. You guys might think, hey, but Regina isn't a first born. But she actually is.Yes, Zelena is Cora's First Born, but she's also Jonathan's first born. (He's her father, see season 3 ep.18 Bleeding through). Regina is Cora's second born, but Henry's first born. And then, again, she's proven to be a savior once! (Season 3 ep. 19. Acurious Thing).
Third Proof - Well, isn't it obvious?! Emma is Snow and Charming's first born, and she's a savior! I believe, that if it wasn't for the Dark Curse that Regina casted, it could be that the Black Fairy would try to abduct Emma. It could be that Rumple knew it, but he knew then that Emma was his key to find his son. (Maybe even defeat his own mother, which he deeply wanted).
But, what makes Emma really the one to destroy the Black Fairy? There is a ten time worse curse on Storybrooke now! Could she be able to break it alone, it just doesn't make any sense! Why would one lousy Savior would be able to defeat the most dark being? If it's a ten time worse curse, it may need more saviors to break. There could be more saviors to show up. Possibly new characters.
Well, if my theory is right, there is someone we weren't taking a possibilty for as a savior that might show up. There were a few babies that were able to escape the Black Fairy. Emma, Regina, Aladin.
There is a possibilty of another one that we know, but not know his name.
In episode 9 ('Changelings'), Rumple collects a baby which he doesn't know his name, and don't care to know. He succeeded to tempt the Black Fairy to come out with the baby.
Well, if my theory about the abducted babie's being savior's or possible ones, it could be that the specific baby is an unknown savior.
-- of course he'd be older, because it happened a lot of years ago...
They did confirm in an interview that the baby might show up again
It could be, that Alladin calimed his destiny to be a savior again somehow, and help. And if so, it could be that Rumple would still have a chance to claim his destiny as the savior back! (Emma, Regina, Aladin, Rumple, baby grown up) We now have five possible saviors that might join to defeat the Black Fairy. It could be that Zelena is a possible savior too. (Actually, about that I'm not quite sure...but who knows... eh, whatever )
So, only the next episode would confirm if i'm right. I can't wait for the Final to come
I hope that maybe someome finds my theory interesing. Feel free to comment. I'm open to criticism.