I'm still not a fan of the introduction of new versions of the stories we know. To me, the show has always been about how all these stories "really" happened, so seeing that they're not the one true version in the OUaTverse is weird. Does it mean that all stories and their adaptations exist in the OUaTverse? Anyway, here's a theory that I'd like to see.
"What's the harm of letting a not-real me out of a not-real prison into a not-real world, hmm?" asked fake Rumplestiltskin in the Wish Realm. I hope the answer to this question will come next season. We're talking about Rumplestiltskin. Once Regina freed him, can we really expect him to settle for his single reality when he has just learned there are actually multiple versions? He particularly acknowledged that there must be several versions of himself out there: "Well, dearie, on behalf of all Rumplestiltskins everywhere, I'm here to make good on my word."
Whether it be to find a living Baelfire or Belle in other versions of their story, to conquer all the realms, to absorb de power of other versions of the Dark One, or something else entirely, I think the only way Rumple would proceed after learning this information is to try and visit other versions of the story.
My theory is that Wish Realm Rumple could team up with one or two other Rumplestiltskins (perhaps one of them is even named Rumpelstiltskin) from other versions of the Enchanted Forest.
I think the whole "new version" is probably perceived in an odd way. Most seem to put it as "versions of Cinderella", but I think it's probably not what Adam and Eddy are intending. I'll give two examples of what I think they are getting at:
A. Briar Rose and Aurora
They are versions of the concept/story of "Sleeping Beauty". So....
B. Jace and Ella
They are versions of the concept/story of "Cinderella". Then, Jace isn't some alternate Ella, or Dania isn't recasted to play Jessy's Cinderella, but they both share a similar conceptual background that anyone in the audience will see it as Cinderella.
The writers seem to hint that each book might have a version of these concepts/stories, but they are stories of different individuals who are not necessarily related.
So, I'd think:
Versions of Once's Rumple: Rumple (Mr. Gold, Book Rumple), Wish Realm Rumple....but
Versions of "Rumpelstilskin/Trickster/Devil/Imp": Rumple, Loki, Mephistopheles
Of course, those examples are just there for show, but I think that's more what they are doing. So, there could be a new guy called Rumpelstilskin, but there would be no beloved Belle and no Baelfire because they aren't the same person, but have the same concept/story basis.
Like, for instance, post-7th Dark Curse, Spindleshanks was a dwarf that peddled in fairy dust. After stealing a wand, he starts making deal. Eventually he makes a deal with a miller/farmer/peasant's daughter, etc, etc. So, he'd be "Rumpelstilskin", but not Rumplestilkin (OUAT Seasons 1 to 6) or a alternate-reality version.