Sua pergunta é dupla.
is there any official mention of which version the Blade Runner 2049 uses as its definitive source?
Na verdade não.
A melhor "menção oficial" está em esta entrevista Collider, onde o diretor Denis Villeneuve tem a dizer (versão em texto da parte relevante citada em este artigo ScreenRant):
I think honestly I would recommend seeing the very, very final director’s cut of Ridley’s. If they are curious enough, for me, it’s like the very first cut that was released in 1982 with the voice over and the very last one. The one with the voice over is the one that I was raised with, that made me discover this universe. At the time, I was not aware of the controversy… I saw the movie in a small town in Canada, there was no internet at the time, so I didn’t know that critics didn’t welcome the movie well. I just deeply loved the movie at first sight, and for me, the voice over had that kind of noir quality, so it’s not something that shocked me, I embraced it at the time.
Now, I understood, much later, when I saw Ridley’s final director’s cut, I understood where he wanted to go and what he was missing. Then, I became a fan of it, so my favorite version is the final director’s cut from Ridley.
Este "corte final do diretor" é o 2007 Final Cut. Então aí está: O diretor de Blade Runner 2049 acha que você deveria ver o Final Cut of Blade Runner - porque é o favorito dele.
Isso não significa que ele usou o Final Cut como sua fonte definitiva para a sequência, no entanto. Esta resposta no Movies & TV Stack Exchange, mencionado nos comentários acima, tem algumas citações mais interessantes de Villeneuve. Vou citar aqui na íntegra:
So when Blade Runner 2049 director Denis Vileneuve met with reporters at San Diego Comic-Con, someone inevitably had to ask which version of Blade Runner is Blade Runner 2049 a sequel to. "The thing is that I was raised with the first one," Vileneuve said, referring to the original theatrical cut. "There was one Blade Runner at the time. I remember seeing the first movie and falling deeply in love with it."
But his love for the original doesn't mean that there isn't room for nuance, or that he can't acknowledge the intent of Scott's later versions of the film. "The key to making [Blade Runner 2049] was to be in between," Vileneuve said. "[The theatrical version] is the story of a human falling in love with an artificial being, and the story of [the director's cut] is a replicant who doesn’t know he’s a replicant and slowly discovers his own identity. Those are two different stories."
In order to tell his story without alienating fans who prefer one version of the story, the director went back to the source material, Philip K. Dick's Do Androids Dream of Electric Sheep? for inspiration. "I felt that the key to deal with that was in the original novel," Villeneuve said. "In the novel the characters are doubting themselves and they aren’t sure if they are replicants or not. From time to time the detectives are running scans on themselves to make sure that they are human. I love that idea so I decided that in the movie Deckard is unsure, as we are, of what his identity is. I love mystery."
As for which version Harrison Ford and Scott consider to be the truth? "Harrison and Ridley are still arguing about that," Vileneuve says. "If you put them in the same room, they start to talk very loudly about it."
Portanto, isso é vago, mas a conclusão é que o Corte Teatral e o Final Cut (os dois únicos cortes principais do filme) contam duas histórias diferentes, e Villeneuve não queria considerar um deles mais cânone do que o de outros.
Agora, para sua pergunta subjetiva:
what version of the original Blade Runner should I have seen in order to be up-to-date with Blade Runner 2049?
Na minha opinião: isso não importa.
É importante ter visto a versão Blade Runner entender várias referências e pontos de plotagem Blade Runner 2049. Entretanto, nenhum desses pontos da trama é exclusivo para nenhuma das versões do filme original. A trama aponta que estão exclusivo para o Final Cut não é tão importante na sequência, nem é desconsiderado.
O final de Blade RunnerO Final Cut é mais ambíguo que o final do Theatrical Cut. Eu realmente não posso discutir os detalhes disso sem estragar os dois filmes, mas direi que acho que o Final Cut é um filme muito mais interessante que o Theatrical Cut, mesmo que a ambiguidade possa ser um pouco resolvida pela sequência. Spoilers para o final de Blade RunnerAs duas principais versões:
In the Final Cut of Blade Runner, it's implied that the blade runner Rick Deckard himself might be a replicant. In the Theatrical Cut, there's nothing to imply that he's anything but a human.
A sequela parece resolver essa ambiguidade. Spoilers para 2049:
We meet an older Deckard who has aged like a human. There's no mention of him being a replicant.
Superficialmente, isso parece estar de acordo com o final do Corte Teatral e desconsiderar a ambiguidade levantada pelo Corte Final. No entanto, a ambiguidade ainda existe, se você esticar um pouco a cabeça. E se eu entendi Villeneuve corretamente na entrevista de Collider que citei no topo, é exatamente o que ele pretendia que fizéssemos para se encaixar nas duas versões. Spoilers para várias partes do 2049:
Deckard has lived in an irradiated area for years, seemingly without having taken any damage. It's also not clear to me whether Tyrell's experimental replicant breeding program was meant to allow humans to breed with replicants, or simply to allow replicants breeding with replicants (by biological definition, are the more advanced replicants the same species as humans, and can interbreed with them, or not?). In his meeting with Deckard, Wallace seems to imply that Tyrell might have set up Rachael and Deckard's romance in order to make them procreate, a scenario which works either way, but perhaps best if Deckard is a replicant that Tyrell could, in some capacity, control.
Tudo isso dito, eu concordo com Villeneuve em que eu recomendaria assistir o Final Cut do filme original.