In itself, the “dream” (if that’s what it is) means nothing. Or it could mean *anything*, depending on how you look at it. It does not *seem* connected to anything else in the movie – anything, *except* Gaff’s final origami “message”, which happens to be (of all things) a unicorn!
Now, all the origami figures seem to be comments from Gaff about Deckard. (See question “What do Gaff’s origami figures mean?”)
Therefore it seems logical to assume the unicorn is a reference to Deckard, and to his unicorn “dream” as well. So Gaff seems to know Deckard’s inner thoughts, suggesting the “dream” would actually be an implanted memory or image. This strongly suggests Gaff knows Deckard’s [implanted] memories, just like Deckard knew all about Rachael’s. Of course, purely within the fictional reality of LA2019, there are a multitude of other possibilities for the meaning of unicorn dream/origami. It seems clear that Gaff could not know that Deckard had just had his unicorn dream a short time earlier, so this must necessarily refer to a general memory/dream that Deckard has and which Gaff knows about, perhaps from Deckard’s file. But of course that is then just as applicable if Deckard is human.
The whole unicorn thing was one of the clues Ridley Scott inserted in order to create a “surprise revelation” concerning Deckard’s true nature… (See question “Is Deckard A Replicant”) And in fact, it was the idea of the unicorn “calling card” that developed into the idea of Gaff making his origami figures.
Posted in: 4.5. Deckard