Like everything in the Star Wars universe it seems like it was all “made up as they went along” with a follow-up of “we always meant to do this” or concocting some way to rationalize it all.
I know this is not 100% proof-positive, but the level of circumstantial evidence is off the charts here to support the claim that none of the topic of this specific question was ever planned and it was all decided on as part of pre-production for this specific film; aka: The Rise of Skywalker.
One of the biggest fallacies of the Star Wars universe is that all of the intricacies, connections, specifics and details are very well planned out.
That really has never been the case. For example — and as elaborated in this answer I posted on the Movies/TV Stack Exchange site — the whole “Luke and Leia being siblings” thing really only was developed when Return of the Jedi (1983) was in pre-production. Heck, in Star Wars (1977) and The Empire Strikes Back (1980) Luke and Leia were being portrayed as romantic interests. Why else would Leia give her “brother” (Luke) a big, full mouth French kiss in The Empire Strikes Back if any of this was planned out?
But back on topic…
Disney has generally been vague about whether stories are well planned out in advance, but I found a few good examples of people involved with the production vaguely answering — and never implying — that any of this was planned; quite the opposite.
Here check out this obtuse quote from writer/director J.J. Abrams in CinemaBlend (December 22, 2019); bold emphasis is mine:
“This whole trilogy — this 7, 8, and 9 — is really about the generation that sort of follows the great generation and the idea of balance, bringing balance to The Force. Which is the whole point of the chosen one Anakin in the original trilogy. What I love was the idea that balance brought to The Force doesn’t mean it’s forever. It’s not immediately everlasting. And I think the idea that if we are not careful, the evil will rise again. That we have to be proactive in doing what we can and maintain the balance, and how does the generation that follows the great generation do that. And the idea that these two main characters, both the grandchildren of these crucially important characters of Palpatine and Skywalker — as [co-writer] Chris [Terrio] was saying, these two houses coming together in this next generation felt like there was an inevitability to it. And if one were to watch [Episodes] 1 through 9, you know, 50, 100 years from now, hopefully you feel that these stories were inevitably leading there.”
Then there is this quote from producer Michelle Rejwan from Gizmodo (December 6, 2019); again bold emphasis is mine:
“I think there was a feeling of inevitability that Palpatine had been a part of all three and in the biggest picture of nine movies, he has been there from the very beginning. And his presence in this movie, we will not spoil that, but when you see it it does feel to us, not only does it have the feeling of inevitability, but the ending of where we left him last, in Return of the Jedi, was very important to J.J. and Chris and to all of us. We discussed it at great length. So no, I don’t think so. I think it definitely feels as though it is in the DNA of the nine. And it felt appropriate to have his presence be in this movie.”
Then there is this info on from actor Ian McDiarmid who plays Palpatine on ComicBook.com (December 22, 2019) from an interview with Digital Spy (December 19, 2019); yet again bold emphasis is mine:
“I thought I was dead! I thought he was dead. Because when we did Return of the Jedi, and I was thrown down that chute to Galactic Hell, [he was dead]. And I said, ‘Oh, does he come back?’ And [George] said, ‘No, he’s dead.’ [Laughs] So I just accepted that. But then, of course, I didn’t know I was going to be doing the prequels, so in a sense he wasn’t dead, because we went back to revisit him when he was a young man. But I was totally surprised by this.”
And more for ComicBook.com (December 14, 2019) as well:
“It was a total surprise when about a year ago I had an email from J.J. saying, ‘Is there a good time to call you? And where should I call you?’” McDiarmid recalled. “So I emailed back and said, ‘Such and such time, and this is the best phone number to get me.’ And then he called me straight away and said, ‘We’re thinking of bringing back the Emperor. How do you feel?’ So I controlled myself and said, ‘Sounds like a great idea!’ And I realized my voice had shot up there, and I thought, ‘He won’t be able to cast me if I speak like that.’ I said, ‘Well, that’s wonderful.’”
None of this sounds like there was a definite plan, which is the line that George Lucas always gave when he answered similar questions about the prequels. If anything it sounds like they are trying to over rationalize it all.
But back on the topic really… Of Rey’s lineage.
Based on those quotes above and the revelation surrounding Rey seems to be improvised at best. Meaning The Rise of Skywalker seems to be a retcon of not just key points in The Last Jedi but also The Force Awakens.
I mean why bring back J.J. Abrams to do this if this final film of the main “Skywalker Saga” if this was all well so well planned to begin with?
