There are plenty of theories, conspiracy and otherwise, about Stanley Kubrick's The Shining and Ridley Scott's Blade Runner. The Shining's hidden messages now have a whole film dedicated to them: Room 237. Both The Shining and Blade Runner are highly regarded, thematically complex, and nebulous in meaning - ingredients which make both ripe for speculation on multiple layers of understanding. And it just so happens that the closing shot of Blade Runner is (quite literally) the opening shot of The Shining. What if that isn't a coincidence - what if The Shining is the sequel to Blade Runner?
Spoilers for both movies here on out - although if you haven't seen one or both, you should make a point of doing so now.
Let's suppose for a moment that, unlike imdb tells us, that Scott only borrowed footage from the Shining for Blade Runner after the studio didn't like his original bummer of an ending. And let's ignore the fact that the movies were released out of order (The Shining first). Instead, let's consider that Jack Nicholson was considered for the role of Deckard, and that Harrison Ford was considered for Jack Torrance (also per imdb). Movies have long production cycles, and just because they finished at different times doesn't mean the directors didn't collude earlier in the process. And even what little we "know" about both movies, their productions, and their creators' intentions is inconsistent - one of the reasons conspiracy theories have room to grow and flourish.
Blade Runner ends with Deckard and Rachael riding away from future Los Angeles off into "the wilderness." That wilderness is the same that Jack and Wendy Torrance ride into at the start of The Shining, the two films' shared footage and the bridge between the stories. In between films, Deckard/Jack and Rachael/Wendy have a child, Danny - something that replicants shouldn't be able to do, but Rachael/Wendy is special already (as Gaff implies), having lived past her expiration date.
The first quarter or so of The Shining is very focused on two prolonged interviews that Jack and Wendy undergo. These interviews bear a striking resemblance to the Voight-Kampff tests administered in Blade Runner to determine if the subject is human: the questions and statements are delivered deadpan by the interviewers, are administered across a desk/table, and are designed to test the subjects' emotional responses. In Jack's case, he is interviewing for the job of caretaker and is presented with the fact that the previous caretaker killed himself and his family; Jack fails the test, reacting with a smile and nonchalance instead of concern (confirming that yes, Jack/Deckard is a replicant). Wendy, interviewed by the doctor checking on Danny, is asked to describe her son's accident. She is casual about the event, although true to Rachael's prior demonstrations, she still does better at pretending to be human than her husband.
Once in the Overlook Hotel, The Shining starts playing with ideas about past lives and memory. Jack feels as though he's been in the hotel before, Grady tells him he has always been the caretaker, and as we know from the end Jack really has been there before - the photo suggests perhaps in a previous life. Or more compellingly, maybe it's Jack's original that's in the photo, the one that Jack has been replicated off of. Jack's memories are that of the original caretaker, ones that have been written over for his purposes in his current Jack/Deckard incarnation. This is supported by the inclusion of Joe Turkel as the Overlook's ghostly barkeeper Lloyd - the same actor who played Dr. Eldon Tyrell, the creator of the replicants in Blade Runner. Perhaps his appearance is as a memory of the original Tyrell, while the Tyrell in Blade Runner was a replicant (something that the Blade Runner wiki indicates was originally planned). The Tyrell from Blade Runner is his own replicant, using the same process that he used to create Rachael using his granddaughter.
Then there are the striking similarities between Roy Batty's hunt of Deckard and Jack's hunt of Wendy and Danny. Both Batty and Jack regress to animal howls and mad raving - and iconically, they both break through a door/wall and stick their faces through the hole. Both fail in their chase and die slowly in the sitting position.
But why would Jack/Deckard end up like Roy Batty? Perhaps it's because of replicant's eventual inability to process their feelings; Jack is erratic with his wife and son, his responses incongruous with situations. Or perhaps it is just his nature as the kind of replicant he is: Jack/Deckard is a replicant built to hunt replicants, and he's finally giving in to his programming just as he couldn't resist the call to track down Roy Batty and the other Nexus-6. As Jack/Deckard tells Wendy: "Did you ever think of my responsibilities?!"
The two are certainly discrete movies, but in many ways The Shining is the unhappy ending that Ridley Scott really wanted for Blade Runner.